WASHINGTON - The killing of al-Qaeda's No. 3 leader is unlikely to derail the terror group for long.

Pressured by American drone missile strikes, the extremist network has shrugged off similar losses of its top-tier leaders and is increasingly relying on new franchises that threaten attacks on the United States.

The death of Mustafa al-Yazid strikes a short-term blow to a terror group that still has multiple tentacles to continue the fight.

With offshoots in Yemen, Somalia, North Africa, and along the Afghanistan-Pakistan border, al-Qaeda has become a more fragmented enemy. And, as shown by the Christmas Day airliner attack, its franchises are becoming more independent, more dangerous, and equally intent on targeting America.

Even as the United States eliminates al-Qaeda leaders, the terror group is rapidly inspiring recruits who are just as eager to attack and kill Americans.

"While we're having some success in putting pressure on them, they're also having a great deal of success radicalizing other parts of the global Islamic jihadist movement to join them in attacking the United States," said Bruce Riedel, a senior fellow at the Brookings Institution Saban Center and a former CIA officer.

Yazid, who is also known as Sheikh Saeed al-Masri, is the seventh person considered by U.S. intelligence to be the No. 3 leader who has been killed or captured since 2001, Riedel said. "It shows that it's been two things - a very dangerous job, and, secondly, one that you can refill relatively easily," he said.

Yazid, whom al-Qaeda described as its top commander in Afghanistan, was killed along with his wife, three daughters, a grandchild, and other men, women, and children, the group said. He is believed to have been struck down by a CIA drone strike, likely in the last two weeks.

Among Yazid's predecessors in the third spot were Khalid Sheikh Mohammed, the reputed mastermind of the Sept. 11 attacks, who is held in the Guantanamo Bay, Cuba, detention center.

U.S. officials agree that al-Qaeda has become proficient at replacing its vulnerable No. 3 tier. But they also assert that the loss is a severe setback for a group that has relied on Yazid as a founding member of al-Qaeda and the group's prime conduit to Osama bin Laden and Ayman al-Zawahiri. He also ran al-Qaeda's day-to-day operations and had a hand in the group's financing, according to U.S. officials.

The success of the drone strikes has made it harder for bin Laden and his lieutenants to operate and find haven.

U.S. intelligence officials say al-Qaeda has been weakened, both financially and structurally, over the last few years. The terror group is "under more pressure, is facing more challenges, and is a more vulnerable organization than at any time" since the Sept. 11 attacks, said Mike Leiter, director of the National Counterterrorism Center.

Leiter told Congress that al-Qaeda havens in Pakistan were shrinking and that the terror group's leadership losses had hurt its training and plotting.

But its allies, like al-Qaeda in the Arabian Peninsula and al-Shabab in Somalia, remain resilient. In its announcement of Yazid's death late Monday, al-Qaeda issued a blunt warning.

"What he left behind will, with permission from Allah, continue to be generous and copious and to produce heroes and raise generations," the terror group said on jihadist websites.

In fact, U.S. officials are increasingly warning that al-Qaeda's outlying, smaller franchises are more likely to plot and wage off-the-cuff, less sophisticated attacks that are harder to detect and prevent.