WASHINGTON - The Obama administration has formally notified the sale of eight F-16 combat jets to Pakistan while a US senator plans to force senators to vote on the State Department’s approval of fighter planes to Pakistan using an obscure Senate rule that hasn’t been invoked in decades.

The publication of the federal notification of the sale on Saturday said: “This proposed sale contributes to US foreign policy objectives and national security goals by helping to improve the security of a strategic partner in South Asia.”

The cost of the F-16s is estimated to be nearly $700 million, the notification said, adding the Pakistan government had requested the sale.

The US notification said the sale involved the release of “sensitive technology” to Pakistan. The jets are equipped with advanced avionics, a digital flight control system and external electronic warfare equipment.

But Senator Rand Paul, who ended his bid for Republican presidential nomination earlier this year, is invoking the obscure Arms Export Control Act of 1976 in a bid to shoot down the sale with a resolution of disapproval, according to Politico, a conservative newspaper.

"Over the last few years we have seen that Pakistan is an uncertain ally when it comes to cooperating with the United States,” Paul said in a statement. “As I travel in Kentucky (his home state), I meet countless individuals who are struggling to survive in this economy, we have no business sending hundreds of millions of dollars overseas."

The last time the Senate voted on such a resolution, according to Politico, was in 1986, when then-Senator Alan Cranston, a Democrat, forced a roll call vote on banning sales of certain missiles and defence services to Saudi Arabia.

Paul introduced the resolution that would block the sale of the F-16 aircraft to Pakistan on Feb 25, two weeks after the administration announced it had approved the potential sale.

The senator is using a little-known provision in the Arms Export Control Act of 1976 that allows any member of the Senate to secure a floor vote to disapprove an arms sale. Under the law, the senator must introduce a resolution of disapproval, and then wait 10 days for the Senate Foreign Relations Committee to act on the measure, according to the Congressional Research Service.

If the committee doesn’t take up the measure after 10 days, the senator can move to discharge that resolution from the committee with a floor vote. That vote is primarily procedural, and not necessarily an up-or-down vote on the resolution’s merits.

Citing one senior Republican, Politico said it was likely that Paul would get such a vote on the floor sometime before the next recess, which begins the week of March 21, in between other Senate business.

Paul has frequently criticised foreign aid to Pakistan and other countries. In 2012, he introduced legislation to end all US aid to Pakistan in protest of the arrest of the Pakistani doctor who helped the US track down Osama bin Laden.

Secretary of State John Kerry defended the fighter jet sale to Pakistan in a House hearing last week, saying Pakistan could do more to combat terrorism but arguing the F-16s were important to their fight.

“The F-16s have been a critical part of the Pakistani fight against the terrorists in the western part of that country, and have been effective in that fight,” Kerry told the House Foreign Affairs Committee.

Senate Foreign Relations Committee Chairman Bob Corker allowed the Obama administration to proceed with the deal, but said he would not approve using US funds to pay for the planes through the foreign military financing (FMF) programme.

Corker told Secretary of State John Kerry in a letter last month that he was concerned about Pakistan's ties to the Haqqani network, a militant group that US officials have said is behind attacks in Afghanistan.

In the House of Representatives, Republican Congressman Dana Rohrabacher has introduced a companion resolution disapproving of the arms sale.