ISLAMABAD (AFP) - Pakistan on Monday criticised the United States (US) over legislation linking US$33 million (S$42.1million) in aid with the release of a doctor who helped the CIA track down Osama bin Laden, saying it was "disappointed" by the move.

Shakeel Afridi is awaiting retrial on a treason conviction under the country's tribal justice system for alleged ties to militants.

Angry lawmakers in the US saw his original sentence as retaliation for the raid on Al-Qaeda leader bin Laden's Pakistan compound, and had threatened to freeze millions of dollars in vital aid to the country.

On Jan 17, President Barack Obama signed into law the Consolidated Appropriations Bill 2014, which covers a raft of policies including State Department aid to Pakistan.

The bill states: "Of the funds... that are made available for assistance for Pakistan, $33,000,000 shall be withheld from obligation until the Secretary of State reports to the Committees on Appropriations that Dr Shakil Afridi has been released from prison and cleared of all charges relating to the assistance provided to the United States in locating Osama bin Laden".

Afridi was arrested after US troops killed bin Laden in May 2011 in the northwestern town of Abbottabad. Islamabad branded the raid a violation of sovereignty, and relations with the US fell to an all-time low.

The doctor had been recruited by the CIA to run a vaccination programme in Abbottabad in the hope of obtaining DNA samples to identify bin Laden, although medics never managed to gain access to the family.

Afridi was convicted not for working for the CIA, for which the court said it had no jurisdiction, but for alleged ties to militants.

The Pakistani foreign ministry in a statement on Monday said it was "disappointed" at the condition.

It said that Afridi, a citizen of Pakistan, was accused of having violated the country's laws.

"His action also caused immense damage to the polio campaign in the country. His case is sub judice and he remains entitled to due process under the law," it said.

"Consequently, any linkage of US assistance to this case is not in keeping with the spirit of cooperation between the two countries."

The statement added that Pakistan and the US were engaged in building a close, cooperative relationship, and that it hoped the process could move forward in a "constructive manner".

In November, Pakistani authorities unexpectedly charged Afridi with murder and fraud over the death of a patient some six years earlier.