The 2026 World Cup has not even begun, but it is already shaping up as one of the most contentious tournaments in football history.

Fifa president Gianni Infantino has called the first World Cup staged across the United States, Mexico and Canada “the greatest event that humanity, that mankind, has ever seen.” For Fifa, it is meant to be the biggest, most inclusive and most profitable edition of the tournament.

For critics, other words come more easily: the most politicised, the most expensive, possibly the hottest, the most polluting — and certainly the most lucrative for Fifa.

The tournament opens on Thursday in Mexico City, where Mexico face South Africa at the Estadio Azteca. The stadium will make history as the first venue to host the opening match of three different World Cups.

But even there, the mood is not only festive. Protests by teachers demanding higher wages have already reached the area around the stadium, and World Cup statues in the city have been toppled.

Mexico offers a preview of the larger tensions around the tournament. The country is dealing with security concerns after a year of cartel violence. The United States, where about three quarters of the matches will be played, is facing criticism over immigration policy, visa restrictions, ticket prices and the role of Donald Trump.

Canada, the third host, is part of a tournament being staged amid wider disputes between the co-hosts over trade, migration and security.

The 2026 World Cup is unprecedented in scale. No previous tournament has been spread across three countries.

None has included 48 teams and 104 matches. But its political context is just as unusual. For the first time, a host country is at war with a participating nation.

Iran’s presence has become one of the clearest examples.

Fifa confirmed last month that Iran had moved its team base from Arizona to Mexico after the military campaign launched in February, when the United States and Israel attacked Iran and triggered retaliatory strikes across the Middle East. Although a ceasefire came into effect in April, attacks between the sides have continued.

Donald Trump at one point said it was not “appropriate” for Iran to take part “for their own life and safety.” One of his envoys even suggested that Iran should be replaced by Italy, who failed to qualify.

Iran is still expected to play in its fourth consecutive World Cup. But the country has accused the United States of denying visas to some officials and backroom staff.

One Iranian official said players had been told they would have to enter and leave the US on the same day for their three group matches there.

Iran’s football federation also said its allocation of fan tickets for the group stage had been revoked, calling it a sign that political considerations were interfering with the world’s biggest football event. Fifa said it was working to give Iranian supporters as many chances as possible to attend matches.

The dispute has widened beyond tickets and visas. Iran has threatened to stop its matches if unauthorised flags are shown or slogans targeting the national team are chanted in stadiums. The issue is especially sensitive because Iran’s first two games are in Los Angeles, home to a large Persian community.

Immigration restrictions have become one of the defining controversies of the tournament.

During Trump’s first term, Infantino warned that travel bans could threaten a country’s ability to host the World Cup because qualified teams, officials and supporters must be able to enter.

Now, under Trump’s second-term immigration policies, fans from Iran, Haiti, Senegal and Ivory Coast face full or partial travel bans.

BBC analysis found that supporters from more than a quarter of the 48 competing countries face travel bans, tighter restrictions or high visa rejection rates. Journalists have also reported problems obtaining visas, and Somali referee Omar Artan was removed from the list of World Cup officials after being denied entry to the United States.

Craig Foster, a former Australia captain and now a human rights campaigner, called it “a deeply politicised World Cup.”

He said the idea that sport can be separated from politics should no longer survive this tournament.

The United Nations has also entered the debate. UN human rights chief Volker Türk called for a “massive re-think” of how US immigration enforcement affects human rights and dignity, especially during the World Cup.

At the same time, the tournament is becoming a showcase for Trump. The United States is marking the 250th anniversary of American independence, and Trump is expected to be highly visible throughout the event. Infantino’s close relationship with him has drawn scrutiny, especially after the Fifa president awarded Trump a “Fifa Peace Prize” at last year’s World Cup draw.

Human Rights Watch has described the tournament as a potential “bonanza of sportswashing,” while Amnesty International warned that it could become “a stage for repression,” citing immigration enforcement and mass detention in the United States.

The White House World Cup Task Force rejects such criticism.

It says the tournament will be “the safest, and most welcoming sporting event in history” and will show America’s hospitality, security and “spirit of excellence.”

Security will be one of the biggest tests. The Department of Homeland Security, which is involved in the tournament’s security operation, was only recently reopened after a funding dispute.

Andrew Giuliani, who leads the White House World Cup Task Force, said local law enforcement faces an “unprecedented” challenge over the 40-day tournament.

There are other risks too.

Authorities are monitoring concerns over an Ebola outbreak centred on the Democratic Republic of Congo, whose team is due to play in Houston, Atlanta and Guadalajara.

The US State Department said it is coordinating measures to protect citizens, visitors, fans, athletes and tourists.

The cost of attending the World Cup has caused another backlash. When the North American bid was submitted in 2018, organisers said the most expensive ticket to the final would cost $1,550.

When tickets went on sale to official supporters’ clubs, the highest price was $8,680.

Supporters’ groups called the prices a betrayal.

Fifa later announced a small number of $60 tickets, but the use of dynamic pricing — where prices change depending on demand and timing — has angered fans.

On Fifa’s official resale platform, the organisation takes a 30% fee from each ticket sold.

Officials in New York and New Jersey have opened an investigation into ticket sales, with Fifa accused of misleading fans and artificially inflating prices. Fifa says more than five million tickets have already been sold and that demand remains strong.

Yet BBC Sport found thousands of tickets for matches involving smaller nations available below face value on resale platforms.

There are also signs that high prices have discouraged travel. Hotel bookings in many host cities are below expectations, and supporters’ groups say many fans have simply been priced out.

The costs go beyond match tickets. Train fares from central New York to MetLife Stadium in New Jersey, where the final will be played, rose from a usual $12.90 to $150 before being cut to $98.

The governor of New Jersey blamed Fifa for refusing to subsidise transport.

Fifa also angered fans by announcing that reusable water bottles would not be allowed inside stadiums. Critics said that in extreme heat the ban could endanger supporters and looked more commercial than practical.

After pressure from fan groups and politicians, Fifa changed course and allowed sealed disposable water bottles.

Heat is a serious concern. Researchers say temperatures at 14 of the 16 host venues could reach dangerous levels. Scientists have warned Fifa that its current heat safety measures may not be enough to protect players from serious harm.

The environmental cost of the tournament is also under scrutiny. Fifa has pledged to halve carbon emissions by 2030 and reach net zero by 2040.

Using existing stadiums helps, but the expanded format creates a huge travel burden. Aviation is expected to account for 80-90% of the tournament’s carbon footprint.

Environmental groups say this could be the most climate-damaging World Cup in history, generating more than nine million tonnes of carbon dioxide equivalent — almost twice the average of the previous four tournaments.

For Fifa, the financial reward is enormous.

The expanded World Cup in the world’s most commercialised sports market is expected to generate a record $9bn this year alone. That money will help Fifa redistribute funds to national associations and strengthen Infantino’s position before his expected re-election campaign.

The football itself may still deliver.

The 1994 World Cup helped bring the sport into the American mainstream. Three decades later, the United States has stronger domestic leagues, major stadiums and deeper investment in global football.

US Soccer chief executive JT Batson has called the tournament a chance to transform the game in America.

But the build-up has shown how much pressure surrounds the event.

The World Cup is still the world’s biggest football stage. This year, it is also a test of how much cost, politics, heat, security and commercial expansion the game — and its supporters — can bear.