Usama bin Laden and his No. 2 man, Ayman al Zawahiri, are rebuilding the Al Qaeda terror group along the Afghanistan-Pakistan border, but the bases are smaller and lieutenants are less experienced, a U.S. official said Monday.

The American official was confirming a story reported in Monday's New York Times that said a band of training camps has popped up in Pakistan along the Afghan border and the leadership chain of command has been re-established despite an "erosion" of leadership after the Sept. 11, 2001, terror attacks.

"Old hands have been picked off and the new people are less capable and less seasoned," the official said. But "no one suggests Al Qaeda no longer has a command structure or a haven ... though [we] wouldn't call it a safe haven."

In a speech to the American Enterprise Institute last week, President Bush said that across Afghanistan last year, "the number of roadside bomb attacks almost doubled, direct fire attacks on international forces almost tripled and suicide bombings grew nearly five-fold.

"These escalating attacks were part of a Taliban offensive that made 2006 the most violent year in Afghanistan since the liberation of the country."

Last year Zawahiri claimed responsibility for the 2005 London bus and subway bombings and produced a statement by one of the bombers. He is said to be in charge of directing the terror camps.

"I think one assumes that Zawahiri has been more of an operational head and bin Laden has been more of a figurehead and financier over the last several years. [Bin Laden] has not been known for having a detail-oriented operational command," Former U.S. Ambassador to Saudi Arabia Robert Jordan said, adding that knowing the source of the intelligence is the only way to know the extent of bin Laden's participation.

U.S. officials have concluded that tribal leaders in the mountains are protecting bin Laden and his followers instead of going after them as promised in a deal cut by Pakistani President Pervez Musharraf and the local leaders after a failed Pakistani army offensive.

Jordan told FOX News that Musharraf's failure to stop the buildup of terrorists has complicated U.S. efforts, particularly as NATO forces consider the options for disbanding the camps.

"The Pakistanis are very, very angry every time we launch an air strike and there are civilian casualties, so we're walking a tightrope with President Musharraf. He has not been very helpful in this regard. He has made deals with the warlords up there that have turned out not to be very good deals, so there are very few really good options, and air strike may be the choice of last resort," Jordan said.

Since U.S. forces entered Afghanistan in October 2001, 297 troops have died in the region. On Sunday, an additional eight were killed and 14 others wounded when a Chinook helicopter went down. Terrorists tried to take credit for the downing of the plane, but U.S. military officials said nothing indicated an attack on the chopper, and more likely a technical failure caused the crash.

In his speech last week, Bush announced that a NATO-led offensive would begin this spring in the mountains of Afghanistan. The U.S. Army's 10th Mountain Division also conducted two offensives against the Taliban during the winter.

Bush asked NATO countries to send more troops to Afghanistan, announcing the United States will up its force by 3,200 and go after Al Qaeda and the Taliban when the snow melts in the mountain passes.

"This spring there is going to be a new offensive in Afghanistan, and it's going to be a NATO offensive. And that's part of our strategy — relentless in our pressure," he said.

The cross border attacks are souring relations between Afghanistan President Hamid Karzai and Musharraf.

In September, Bush tried to smooth over differences between the two. Karzai said he wants the United States to put more pressure on Musharraf, which U.S. officials fear could be counterproductive. The spring offensive appears to be their alternative.

FOX News' Wendell Goler contributed to this report.