WASHINGTON (AP) -- An apologetic official acknowledged Wednesday that the State Department failed to anticipate the flood of passport applications this year that resulted in long delays and disrupted summer travel plans for many Americans.

"No one is more aware than I am that in the past several months many travelers who applied for a passport did not receive their document in time for their planned travel. I deeply regret that," Maura Harty, assistant secretary of state for consular affairs, told a hearing of the House Foreign Affairs Committee.

She said the department had predicted that passport issuance would rise from 12.1 million last year to 16.2 million this year with the implementation in January of new national security rules requiring those returning by air from Canada, Mexico, the Caribbean and Bermuda to present a passport. Instead, applications are expected to be near 18 million this year, and the normal six-week process for getting a passport ballooned to 12 weeks early this year.

"We failed to predict the record-setting compressed demand," Harty said. "I do sincerely regret that we missed the mark on that number."

That failed to fully satisfy some lawmakers, whose offices have been besieged with calls from constituents panicked that they were not getting the passports they needed for summer trips abroad. Several compared the poor planning -- Congress passed the Western Hemisphere Travel Initiative in late 2004 -- to the lack of preparedness for Hurricane Katrina.

Foreign Affairs Committee Chairman Tom Lantos called it a "national embarrassment." Millions of Americans, he said, "have been reduced to begging and pleading, waiting for months on end, simply for the right to travel abroad."

"It's outrageous, incomprehensible, unconscionable," said Rep. Ileana Ros-Lehtinen, top Republican on the panel. She said her office in Florida had been "flooded with calls from frustrated would-be travelers."

Harty listed several "unknowable" factors for the unexpected surge in applications. She said many people mistakenly believed that the passport requirement also applied to land and sea entry even though that phase of the law will not go into effect until 2008 at the earliest.

She also said that many applicants had no immediate travel plans, and appeared to want passports out of a growing sense that, in a climate of concern over terrorist threats, they need proof of citizenship. "The passport is becoming like some form of a national ID card," she said.