LONDON : Scotland's First Minister has vowed to do "all I can to help" after some Scottish football fans were reportedly denied entry into the United States for the World Cup.

John Swinney said he had contacted US officials in a bid to aid supporters who had their Electronic System of Travel Authorisation (ESTA) permit revoked with less than a week to go before Scotland play their World Cup opener against Haiti in Boston.

An ESTA is usually required for British citizens without a visa going to the US for up to 90 days.

Some members of the Tartan Army, the collective name given to Scotland supporters, reported having their ESTAs revoked at the last minute, leading to some fans seeking emergency appointments with the US Embassy in London.

"I am aware that the United States Embassy has issued advice to individuals affected by ESTA refusals, indicating that they may apply for a visa through the FIFA (football global governing body) pass system and I have asked officials to convey our hope that they can resolve this so that Scotland's fans do not miss out," Swinney told the Scottish Parliament on Tuesday.

"I have asked for specific representations and engagement to be taken forward with the Consul General of the United States in Scotland -- that has been undertaken and we will do all that we can to help out to resolve these issues."

Last week, the BBC reported acting assistant secretary of Homeland Security Lauren Bis as saying the US government's tightening of ESTAs is because "the Trump administration is enforcing immigration laws".

"Under the Visa Waiver Program, all ESTA applications are continuously vetted against law enforcement and security databases," she said. "Travellers must provide complete and truthful information, including all criminal history."

Bis said the "failure to disclose arrests or convictions constitutes misrepresentation" and could lead to "ESTA denial, revocation, or a permanent bar from entering the United States".

FIFA announced Monday award-winning Somali referee Omar Artan has been dropped from officiating at the World Cup after being barred from entering the United States.

Somalia is one of several countries on a travel ban list introduced by President Donald Trump's administration as part of a broader immigration crackdown.