Washington (CNN) -- The United States is watching closely to the see the ultimate fate of the most powerful man in Pakistan, Gen. Ashfaq Parvez Kayani, the Pakistani army's chief of staff. 

Pressured by Washington to crack down on terrorists at the same time he was kept in the dark about the U.S. raid to kill Osama bin Laden, Kayani "is facing more vocal and strident criticism than he has in the past," a senior U.S. military official told CNN. "We really think he is coming under increased scrutiny by junior and mid-grade officers." 

This is the type of scrutiny senior Pakistani generals like Kayani are "not accustomed to facing," the official said. 

Criticism of Kayani inside Pakistan had grown in recent months as he became close to the Obama administration and the Pentagon. But in the wake of the U.S. military raid into Pakistan to kill bin Laden, the criticism has increased from an officer corps furious that U.S. troops invaded Pakistan's territory without the Pakistani military, and especially Kayani, being consulted. 

Adm. Michael Mullen, chairman of the U.S. Joint Chiefs of Staff, is one of Kayani's closest professional and personal allies, having met with him many times in the past several years. 

"Mullen does consider him a friend," said the admiral's spokesman, Capt John Kirby. "That doesn't mean there aren't still disagreements. It doesn't mean Kayani doesn't feel betrayed." 

U.S. officials are closely watching a group known as the "11 corps commanders," the senior Pakistani generals hand-picked by Kayani to command. Keeping their loyalty will be crucial for Kayani to keep his job. 
what was the point of the raid?
about the U.S. raid to kill Osama bin Laden