WASHINGTON: US Secretary of State Hillary Clinton on Thursday denounced as “unjust and unwarranted” the treatment of a Pakistani doctor who was jailed for 33 years for helping in the hunt for Osama bin Laden.

A tribal court in Khyber, a lawless district and extremist hotbed, on Wednesday convicted Shakeel Afridi of treason after he agreed to collect DNA for US intelligence to verify the presence of the most-wanted al Qaeda leader.

“We regret both the fact that he was convicted and the severity of his sentence,” Clinton told a joint press conference with New Zealand Foreign Minister Murray McCully.

The chief US diplomat said Afridi's role “was instrumental in taking down one of the world's most wanted murderers. That was clearly in Pakistan's interest, as well as ours and the rest of the world's.” Afridi ran a fake vaccination program designed to collect bin Laden family DNA from the compound in the garrison town of Abbottabad, near Islamabad, where the al Qaeda leader was shot dead in a US commando raid in May 2011.

The doctor's actions “to help bring about the end of the reign of terror designed and executed by bin Laden was not in any way a betrayal of Pakistan,” Clinton said.

“We are raising it (his case) and we will continue to do so because we think that his treatment is unjust and unwarranted,” she said.

Her remarks were stronger than those given Wednesday by State Department spokeswoman Victoria Nuland who said Pakistan had “no basis for Dr. Afridi to be held.”

Nuland's muted remarks came as Washington and Islamabad, allies in the war on terror, struggle to repair ties that hit a low when US forces staged the secret raid into Pakistan that killed bin Laden.

They were strained to breaking point last November when US forces staged a botched raid that killed 24 Pakistani troops, prompting Islamabad to cut off the land route for supplies to Nato troops in neighboring Afghanistan.

Carl Levin and John McCain, the top senators from the two major US parties on the Senate Armed Services Committee, on Wednesday called Afridi's sentence “shocking and outrageous” and urged Pakistan to pardon and free him immediately.

“Dr. Afridi's continuing imprisonment and treatment as a criminal will only do further harm to US-Pakistani relations, including diminishing Congress's willingness to provide financial assistance to Pakistan,” they warned.

The Senate Appropriations Committee on Thursday voted to cut aid to Pakistan by a symbolic $33 million - $1 million for each year of jail time handed to Afridi.

The measure, an amendment to the $52 billion US foreign aid budget, passed in a 30-0 vote in a sign of growing outrage here over Afridi's conviction.

“We need Pakistan, Pakistan needs us, but we don't need Pakistan double-dealing and not seeing the justice in bringing Osama bin Laden to an end,” said Republican senator Lindsey Graham, who pressed for the measure.

The mammoth appropriations bill, which includes a total of $1 billion in assistance for Pakistan, will go now to the Senate floor after passing out of committee on Thursday.

The reduction represents a 58 per cent cut in the amount of aid President Barack Obama had requested for Pakistan.

The United States has given Pakistan more than $18 billion in assistance since the September 11, 2001 attacks, but US officials have persistent concerns that some elements of the establishment have maintained support for extremists.