For al-Qaeda’s affiliate in Yemen, the volunteer seemed ideal. He was willing to die in a suicide operation, and he had travel papers that would allow him to board a U.S.-bound flight.

It was a perfect dangle, in the parlance of spycraft, and al-Qaeda in the Arabian Peninsula took the bait.

The group’s bombmaker fitted the man with a new version of a nonmetallic “underwear bomb.” What he didn’t know was that the would-be martyr was an agent run by Saudi Arabia. And the man turned the device over to his Saudi handlers inside Yemen.

The Saudis flew the bomb out of the country on a noncommercial jet and handed it over to American officials in an unidentified third country, according to Mustafa Alani, director of security and defense studies at the Gulf Research Center in Jiddah, Saudi Arabia, who has close contacts with the kingdom’s intelligence and counterterrorism agencies. A U.S. official confirmed aspects of his account.

The informant was one of several operatives sent into Yemen over the past two years with Western passports and other documents designed to attract the attention of a terrorist group that is determined to attack the United States, U.S. and Western intelligence officials said Wednesday.

One official described the effort to disrupt the airline plot as part of a broader use of operatives with “clean skins” who can pass themselves off as militants capable of traveling into Europe or the United States.

As part of the effort, the Saudis have used fledgling al-Qaeda operatives who were temporarily detained, as well as individuals who have entered the country’s rehabilitation program, which seeks to turn militants against terrorist groups.

The effort has focused on flipping low-level and aspiring jihadis, according to a former U.S. intelligence official familiar with the operation, which was revealed in news reports Monday.

“There are lots of wannabes who want to know how to shoot an AK-47 but have no intention of blowing themselves up,” said the former official, who like several current and former U.S. officials spoke on the condition of anonymity to discuss sensitive intelligence. “You’re looking for that guy.”

Officials said the Saudi informant used to derail the latest bomb plot had been in place for months.

“This would have been a collection mission — what you’re trying to do is get him in as deep as you can possibly make him go,” said a former CIA official familiar with operations against al-Qaeda in the Arabian Peninsula, known as AQAP. “You don’t send him in there with the purpose of ‘Get a bomb and come back.’ ”

When AQAP leaders tapped the informant for the latest assignment, the former agency official said, CIA and Saudi counterparts assembled plans to use him to recover the device.

The breakup of the bomb plot was followed by an airstrike Sunday that killed a senior militant in Yemen, Fahd al-Quso. He was implicated in the 2000 bombing of the USS Cole, which killed 17 U.S sailors.

Concerns of security, leaks

Rep. Adam B. Schiff (D-Calif.), a member of the House Permanent Select Committee on Intelligence, said the Department of Homeland Security and the FBI are investigating whether changes need to be made at domestic airports or whether protections abroad need to be improved.

“I’m not at all confident about our ability to stop weapons like this,” said Schiff, adding that the security of U.S.-bound planes was of particular concern.

Also Wednesday, U.S. officials said Director of National Intelligence James R. Clapper Jr. had ordered a review of leaks across all 16 agencies in the intelligence community to search for sources of information regarding the airline bomb plot.

Rep. Mike Rogers (R-Mich.), chairman of the House intelligence committee, said on Fox News that additional intelligence “opportunities were lost” in Yemen because of the flow of leaks.

A U.S. official briefed on the case said the Saudi informant in Yemen may have been pulled out of the country prematurely because of concern about public disclosures about the plot. The informant, even after receiving the bomb, was awaiting further instructions, which meant that he was in position to continue providing intelligence for some time, the official said.

“His instructions were to go use” the bomb, “but it wasn’t that he had to go get on a plane the next day,” the official said.

The foiling of the plot revealed the closeness of the U.S.-Saudi partnership in the fight against AQAP. And it showcased the ability of the Saudis to infiltrate an adversary that is as determined to attack the kingdom as it is the United States.

Saudis’ integral role

Saudi Arabia’s chief counterterrorism official survived a 2009 AQAP assassination attempt. The group also launched several unsuccessful operations against key Saudi installations, sending Saudi operatives based in Yemen back across the border to strike at their homeland, according to Saudi and American analysts.

“The Saudis have an ability to operate well against the network, and that’s why they are so critical to this and so deeply involved in these kinds of operations,” said Juan Zarate, who was a counterterrorism official in the George W. Bush administration and is now a senior adviser at the Center for Strategic and International Studies.

The Yemeni group is in some respects an outgrowth of Saudi Arabia’s internal campaign against al-Qaeda that began in earnest in 2003, after deadly bombings in the capital, Riyadh, that targeted compounds used by Western expatriates. A harsh crackdown followed, and the rout of al-Qaeda forced a number of operatives across the border into Yemen.

In 2009, al-Qaeda’s branches in Yemen and Saudi Arabia merged to become AQAP and set up operations inside Yemen. The leader of the group is Yemeni, but many of the other senior operatives are Saudi, and AQAP has continued to attract radicals from the kingdom.

The Saudis have used their vast network of tribal and family connections inside Yemen to infiltrate jihadist cells and tribal communities — something the Americans could never do, Alani said.

In a 2010 plot to down cargo planes, and in the most recent plan, it was intelligence from Saudis inside Yemen that thwarted disasters over U.S. skies, according to American and Saudi officials.

“They’re very good on Yemen because it’s the same tribe, the same language, the same people, the same culture,” said a former CIA official who spoke on the condition of anonymity to discuss the ongoing operation.

The recent political chaos in Yemen, which has allowed al-Qaeda to secure territory in the southern part of the country, has sharpened Saudi concern about its neighbor’s stability. The United States also has stepped up airstrikes against AQAP in recent months, including drone operations.

“Even with the drone strikes, the air raids, the Americans need someone on the ground,” Alani said. “The Saudis are the ones who can pinpoint targets for the Americans.”

Finn and Miller reported from Washington. Staff writer Sari Horwitz and staff researcher Julie Tate contributed to this report