DOHA - Diplomatic foes the United States and Iran face off on the pitch at the World Cup on Tuesday in a match that some Iranians fear may see further run-ins with stadium security or clashes with pro-government fans over raging protests back home.

The contest between the two nations that severed ties over 40 years ago will be held with increased security to prevent a flare up of tensions over the unrest that has gripped Iran since the death in custody of 22-year-old Mahsa Amini on Sept. 16.

In a show of solidarity ahead of the match, which starts at 1900 GMT, the U.S. Soccer Federation temporarily displayed Iran's national flag without the emblem of the Islamic Republic, leading Tehran to complain to FIFA, according to state media.

Qatar, which has strong ties with Washington and friendly relations with Tehran, has staked its reputation on delivering a smooth World Cup, beefing up security at Iran games and banning some items deemed inflammatory, like Iran's pre-Revolution flag.

Iran's top nuclear negotiator Ali Bagheri Kani arrived in Doha on Tuesday on an invitation from Qatar, state news agency IRNA reported without mentioning if he would attend the match.

U.S.-Iranian ties have been especially strained since then-President Donald Trump abandoned Tehran's nuclear deal with world powers. Efforts to salvage the pact under President Joe Biden's administration have stalled.

Politics have spilled into the World Cup, the first to be held in a Middle East country.

Security teams deployed on Friday when Iran beat Wales to "break up a small number of altercations" between Iranian fans outside the stadium, a Qatari official said, adding the incidents were handled "swiftly" to contain tensions.

IRAN TEAM FACES PRESSURE

The Qatar official, when asked about security concerns and complaints over restrictions, said authorities would ensure all matches are "safe and welcoming for all spectators".

Items that "could increase tensions and risk the safety of fans" would not be permitted at stadiums, the official said.

The unrest in Iran poses one of the boldest challenges to the theocracy since the 1979 Islamic Revolution. Washington has imposed sanctions on Iranian officials over the deadly crackdown on protests.

The United States and Iran severed formal relations in 1980 after the Revolution and ties were hostile when their soccer teams clashed in the 1998 World Cup. Iran emerged with a 2-1 victory in a game dubbed the "mother of all football matches".

(Reporting by Maya Gebeily and Charlotte Bruneau; Additional reporting by Elwely Elwelly in Dubai; Writing by Ghaida Ghantous; Editing by Peter Rutherford, William Maclean )