U.S. officials have determined that the Christmas Day bomb suspect spent a significant amount of time in Yemen before attempting to blow up a U.S. airliner Friday — a botched plot that came just days after Al Qaeda in Yemen threatened the U.S., a source tells Fox News.

It is unclear how long 23-year-old Umar Farouk Abdulmutallab remained in Yemen, a hotbed for Al Qaeda training and Islamist activity. At the least, his stay lasted a number of weeks, the source said, but officials believe it could have been for "many months."

A government report sent to law enforcement agencies Sunday noted Abdulmutallab's "extremist ties and possible involvement with Yemen-based extremists." And the 23-year-old Nigerian, who lived and attended college in London, also traveled to many other countries in Europe, a source told Fox News.

Abdulmutallab claimed he received training and instructions from Al Qaeda operatives in Yemen, U.S. law enforcement officials said, and a key American lawmaker has said there are "strong suggestions" of a Yemen connection.

Just four days before the attempted bombing of a Northwest Airlines flight from Amsterdam to Detroit, an Al Qaeda operative in Yemen threatened the United States and said "we are carrying a bomb" in a video posted to extremist Web site.

The video does not contain any clear evidence that the speaker was anticipating Friday's attempt, but it has attracted scrutiny because of evidence of the plot's ties to Yemen.

In the Dec. 21 video, the Al Qaeda operative delivered a eulogy for militants killed in a Yemeni airstrike on a militant training camp four days earlier. The speaker said he had no agenda against Yemeni soldiers, but warned them against cooperating with Americans.

"We are carrying a bomb to hit the enemies of God," the speaker says.

"O soldiers, you should learn that we do not want to fight you, nor do we have an issue with you. We only have an issue with America and its agents, and beware of standing in the ranks of America," he says. "You should not defend these regimes. The soldiers and even Obama cannot put out the light of Islam."

The video was posted on Web sites affiliated with Al Qaeda. The sites identified the speaker as Mohammed al-Kalwi, an Al Qaeda militant reportedly killed in another airstrike on Thursday.

The video showed the bearded militant, wearing a a headdress and green military-style jacket over a long Arab robe, addressing a group of armed followers as he stood atop a car. The followers repeatedly interrupted the fiery address with calls of "God is great."

IntelCenter, a Virginia-based group that monitors extremist activity, said in a report that it was not certain the speaker knew about the airliner plot ahead of time. It said planning for the botched attack likely took place long ago, but it would be plausible for a member with knowledge of the plot to foreshadow an operation.

The United States has grown increasingly concerned about Al Qaeda activity in Yemen, a largely lawless country where militants have been able to organize and train. The U.S. has provided some $70 million in military aid to Yemen this year, and last week's two deadly airstrikes on al-Qaida targets in Yemen were carried out with U.S. and Saudi intelligence help.

Rep. Jane Harman, D-Calif., chairman of a House Homeland Security subcommittee, said there were "strong suggestions of a Yemen-Al Qaeda connection and an intent to blow up the plane over U.S. airspace."

On Saturday, the U.S. Justice Department charged Nigerian Umar Farouk Abdulmutallab with willfully attempting to destroy or wreck an aircraft and placing a destructive device in the plane.

It said Abdulmutallab set off the device as Northwest Flight 253 descended toward Detroit Metropolitan Airport — sparking a fire instead of an explosion.

IntelCenter said staging attacks outside the Arabian peninsula would be a "significant escalation" in activities by Al Qaeda branches based in the area.

It noted that an Al Qaeda magazine in the Arabian peninsula published an article in October that encouraged its activists to make their own explosive devices, and that the necessary ingredients were easily and cheaply available.

It quoted Abu Basir, a reference to Naser Abdel-Karim al-Wahishi, the leader of the Al Qaeda's branch in Saudi Arabia and Yemen, as discussing targets and methods for hiding devices in belts and electronic devices.

He urged militants to target "airports of the Western Crusader states that took part in the war on Muslims, or in their airplanes, residential areas or underground trains."

The Yemeni government said it believed al-Wahishi was attending an Al Qaeda operational meeting in eastern Yemen Thursday when its airplanes hit the group. It is not known whether al-Wahishi was harmed.

Fox News' Mike Levine and The Associated Press contributed to this report.