ISLAMABAD, Pakistan - Few people get to meet the leader of the Pakistani Taliban Baitullah Mehsud, so when Pakistani journalist Behroz Khan was invited to one of his rare press conferences last year, he admits his heart started thumping a little harder.

Baitullah Mehsud has claimed responsibility for many recent attacks in Pakistan.

"You know he's behind the deadliest attacks and these suicide bombers," Khan told CNN. "It is, I would say, a bit scary."

What Khan saw was not the long-bearded, menacing giant he expected. Khan said Mehsud was no more than 5 feet 4 inches tall (1.62 meters), portly, neatly dressed and a bit of a jokester.

"He seemed like a very normal person, cracking jokes and commenting on everything."

But no one was laughing in the U.S. this week when Mehsud vowed to launch an attack on Washington.

In a series of phone calls to the media, Mehsud also claimed responsibility for the recent suicide bombing of a police station in Islamabad and an attack on a police academy in Lahore.

The attacks were revenge, Mehsud said, for U.S. missile strikes on Pakistani soil. Mehsud's threat comes amid U.S. President Barack Obama's call for a crackdown on militants in Pakistan's ungoverned tribal region, Mehsud's home turf. U.S. intelligence officials also put a $5 million bounty on Mehsud's head.

Mehsud's threat may be his answer to Washington, said terrorism analyst Muhammad Amir Rana. Rana is head of the Pakistan Institute for Peace Studies, an Islamabad-based think tank that monitors militant groups in Pakistan.

"I think he wanted to give the message that if you have the head money on me, I can take revenge," Rana said.

Rana said Washington's $5 million bounty entrenches Mehsud as Pakistan's most powerful militant commander and puts him on the world's most wanted list with names like Osama Bin Laden, Ayman Al-Zawahiri and Afghan Taliban leader Mullah Omar.

It was alongside Mullah Omar's Taliban fighters in Afghanistan where Mehsud established a reputation as a fierce fighter in the 1990s. Mullah Omar was so impressed with the high-school-dropout-turned-militant that he named him a regional commander in Pakistan's ungoverned tribal region, Rana said.

Like his mentor Omar, Mehsud demanded never to be photographed. South Waziristan became his stronghold, a place where Mehsud still offers shelter and training to jihadists and Al Qaeda groups fighting U.S. and NATO forces in Afghanistan, Rana said.

Mehsud was declared the leader of the Pakistani Taliban in 2007. Last year, Time Magazine called him one of the 100 most influential people in the world because of the vast network of militants he controls.

Today Mehsud is suspected of being the architect of some of Pakistan's deadliest suicide attacks and the mastermind behind the assassination of former Prime Minister Benazir Bhutto.

Mehsud has denied involvement in the assassination. But Rana and U.S. intelligence officials said they have yet to see evidence that Mehsud is capable of striking beyond the Afghan-Pakistan region.

"Obviously he's challenging the U.S.," said Rana. "But that doesn't mean he'll go to Washington and do everything by himself."

Rana said Mehsud remains a major threat to Pakistan and U.S. forces in Afghanistan.

Journalist Behroz Khan said he doesn't think the joking militant leader he met was kidding when he claimed to have hundreds of suicide bombers and called them his atom bombs.

"He said the infidels have their own nuclear bombs so they are my atom bombs," Khan said.