Washington ? The Bush administration is poised to suspend a major post-9/11 security initiative to cope with increasingly angry complaints from Americans whose summer vacations are threatened by new passport rules.

A proposal, expected to be announced today, will temporarily waive a requirement that U.S. citizens have passports to fly to and from Canada, Mexico, the Caribbean and Bermuda, provided the traveler can prove he or she has already applied for a passport, officials said Thursday.

The temporary lifting of the passport rule is aimed at clearing a massive backlog of passport applications at the State Department that has slowed processing to a crawl, they said. Rep. Heather Wilson, R-N.M., said the suspension would last until the end of September.

Instead of a passport, travelers will now be able to present a State Department receipt showing their passport application is being processed, and a government-issued ID such as a driver’s license.

Under the plan, those without passports would receive additional security scrutiny when they travel, which could include extra questioning or bag checks.

The suspension will give the State Department time to deal with a surge in applications that has overwhelmed its processing centers since the new rules took effect earlier this year. The backlog has caused up to three-month delays in issuing passports and ruined or delayed the travel plans of untold thousands of Americans.

The State Department has hired hundreds of new passport adjudicators, put employees to work around the clock and opened a new processing facility in Arkansas but has still been unable to meet the demand.

Initial hopes that the delays could be overcome were dashed this month when more than a million requests for new passports were dumped at once on the facilities by banks contracted to clear application fee checks, a senior State Department official said.

The passport application surge is the result of the Western Hemisphere Travel Initiative that since January has required U.S. citizens to use passports when entering the United States from Canada, Mexico and the Caribbean by air.

The travel initiative, which next year will require either passports or yet-to-be developed wallet-sized passcards to be presented at land border crossings, is part of a broader package of immigration rules enacted after the Sept. 11, 2001, terrorist attacks.

It has caused deep annoyance, particularly from those who live in border states and make routine, legal crossings into Canada and Mexico for business and pleasure.

Wilson, whose state is on the Mexican border, said she had been calling on State and Homeland Security to implement a suspension for two weeks.

“I said, ‘You need to take action. This is completely screwed up’,” she said. “To say people must have a passport to travel and not give people a passport is right up there in the stupid column.”