US Secretary of State Hillary Clinton has condemned the imprisonment of a Pakistani doctor who helped the CIA track down Osama Bin Laden.
She said the jailing on Wednesday of Shakil Afridi for at least 30 years was "unjust and unwarranted".
Meanwhile, a US Senate committee cut $33m (£21m) of annual aid to Pakistan.
Dr Afridi was tried for treason under a tribal justice system for running a fake vaccination programme to gather information for US intelligence.
Bin Laden was killed by US forces in Abbottabad, Pakistan, in May 2011.
"The United States does not believe there is any basis for holding Dr [Shakil] Afridi. We regret the fact that he was convicted and the severity of his sentence," Mrs Clinton told reporters on Thursday.
She added that she would continue to pursue the issue with the authorities in Pakistan.
The killing triggered a rift between the US and Pakistan, whose government was seriously embarrassed as it emerged Bin Laden had been living in Pakistan.
Islamabad felt the covert US operation was a violation of its sovereignty.
Absent from court
Shortly after the raid on Bin Laden's house, Dr Afridi was arrested for conspiring against the state of Pakistan.
Pakistan has insisted that any country would have done the same if it found one of its citizens working for a foreign spy agency.
Dr Afridi was found guilty in Khyber district, and fined $3,500. If he does not pay the fine his prison sentence will be extended by a further three years.
Dr Afridi, who is now being held in jail in Peshawar, was not present in court so was unable to give his side of the story.
In June, Pakistani army officials told the BBC that some suspects were arrested for helping the Americans refuel their helicopters during the raid. Others were detained because they were suspected of firing flares to guide the helicopters towards the compound.
It is not clear if Dr Afridi knew who the target of the investigation was when the CIA recruited him, or what DNA he managed to collect in the fake hepatitis B vaccination programme.
The idea was to obtain a blood sample from one of the children living in the Abbottabad compound, so that DNA tests could determine whether or not they were relatives of Bin Laden.
The issues of drone strikes and Pakistan's refusal to re-open Nato supply routes to Afghanistan have also recently strained the two allies' relationship.
Pakistan's parliament has called for an end to the use of drones, and says they are an attack on its sovereignty. A drone strike on Wednesday killed four people in the North Waziristan tribal area, security officials said.
The two countries also failed to reach agreement at the Nato summit in Chicago over the supply routes that were closed after a US air strike in 2011 killed 24 Pakistani soldiers.
Islamabad is demanding more than $5,000 (£3,200) per lorry, up from its previous rate of $250, to let supplies flow again.