The US says it will temporarily ease passport rules imposed after 9/11.

The move is aimed at avoiding US citizens' summer travel being disrupted by a broken passport system.

US citizens flying to or from Canada, Mexico, the Caribbean or Bermuda will no longer need a passport as long as they prove they have applied for one.

Officials said the 'record-breaking demand' at passport offices had led to excessive delays of up to three months.

The revised procedures will remain in place until 30 September.

The suspension of the Western Hemisphere Travel Initiative (WHTI) will not, however, affect Americans driving across their country's land borders or those on cruises, as they do not currently require passports.

However, the Department of Homeland Security has said it will demand passports for all land border crossings from January - a move which correspondents say could spark a fresh demand for the identification documents.

In a statement on its website, the State Department said US travellers would be able to enter and leave by air upon presentation of a government-issued photo ID, such as a driving licence, and official proof of application for a passport.

'The federal government is making this accommodation for air travel due to longer than expected processing times for passport applications in the face of record-breaking demand,' it said.

Passport offices around the country have been struggling with a backlog of millions of applications since the WHTI started in January.

An estimated 25 per cent of the US population, or 78 million people, currently hold a passport.

Between March and May this year, the State Department issued more than 4.5 million passports.

Although it said extra staff had been recruited to deal with the surge in demand, toll-free phone lines have reportedly been overloaded and passport offices swamped by desperate applicants who have been waiting for months.

Representatives in Congress welcomed the decision, which they said should have come sooner.

'[The] decision to suspend is simply common sense, and frankly, should have been made months ago,' said Republican Senator Norm Coleman.

Heather Wilson, a Republican Senator from New Mexico, who had pushed for the restrictions to be dropped last month, said: 'To say people must have a passport to travel and not give people a passport is right up there in the stupid column.'

However, Thomas M Reynolds, a Republican congressman from New York state, warned that the temporary measure would compromise border safety.