The largest chunk from this amount, $900 million, is available for reimbursement to Pakistan but almost half of it, $400m, has been put out of its reach. To get those $400m, Pakistan will have to get a ‘good conduct’ certificate from the US defence secretary.

Like a schoolmaster waiving the punishment given to a student, the defence secretary will have to certify that Pakistan is “taking demonstrable” steps against the Haqqani network of Afghan militants.

The measures also include a “sense of Congress that Dr Shakil Afridi is an international hero and that the government of Pakistan should release him immediately from prison”.

Dr Afridi led US forces to the compound where Al Qaeda leader Osama bin Laden was hiding and is regarded in the Western world, particularly in the US, as an international hero.

Passed by the Senate by 92 to seven votes on Thursday and by the House of Representatives by 375 to 34 votes last week, the bill now goes to the White House for President Barack Obama to sign it into law.

The act imposes four conditions on Pakistan to qualify to receive assistance from the restricted amount:

The US defence secretary needs to certify to the Congress that Pakistan continues to conduct military operations that are significantly disrupting the safe haven and freedom of movement of the Haqqani network in Pakistan.

He also needs to certify that Pakistan has taken steps to demonstrate its commitment to preventing the group from using its territory.

The secretary needs to certify that Pakistan actively coordinates with Afghanistan to restrict the movement of militants, such as the Haqqani network, along the border.

And the final certification needs to say that Pakistan has shown progress in arresting and prosecuting Haqqani network’s senior leaders and mid-level operatives.

During the 2016 fiscal year, which ended in October, Defence Secretary Ashton Carter refused to make a similar certification and Pakistan did not get the restricted amount of $300m.

The 2017 act “refocuses security assistance to Pakistan on activities that directly support US national security interests and conditions a significant portion of funding on a certification from the secretary of defence that Pakistan is taking demonstrable steps against the Haqqani network in Pakistani territory”, said Senator John McCain, chairman of the Senate Armed Services Committee.

It allows reimbursement to Pakistan for security activities along the Afghan border, including training and equipment for the Frontier Corps in Khyber Pakhtunkhwa.