The United States government has decided to suspend aid to Pakistan but it remains unclear if the move will change the close but prickly relationship between the two countries.

While American annoyance with its ally is not new, President Donald Trump had "opened an entirely new bargaining space, which is an unexpected positive", Dr Christine Fair, South Asia expert and associate professor at Georgetown University, told The Straits Times.

Pakistan is unlikely to change its strategic calculus in Afghanistan, she added. "Pakistan is not going to give up (its support for) the Afghan Taleban over this money," Dr Fair said.

Mr Uzair Younus, director, South Asia at the consultancy Albright Stonebridge Group, said forthcoming elections in Pakistan would have a bearing on its response.

He told The Straits Times: "With elections coming up (in July), the (Pakistan) government will not want to be seen as succumbing to US demands for a few hundred million dollars which, if the need arises, Islamabad could receive from its strategic ally, China."

State Department spokesman Heather Nauert said on Thursday that the US would suspend military aid until Pakistan took "decisive action" against groups like the Taleban that were "destabilising the region and targeting US personnel".

Reuters news agency, quoting American officials, said at least US$900million (S$1.19 billion) in security assistance would be affected.

The relationship between the US and Pakistan is riven with contradictions. Sixteen years after invading Afghanistan to drive the Taleban out of power in retaliation for their harbouring of Osama bin Laden, who masterminded the Sept 11, 2001, attack on the World Trade Center, the US is still in Afghanistan, battling a resurgent Taleban whose fighters find refuge across the border in Pakistan.

If the US withdraws from Afghanistan, the Taleban, which control a sizeable chunk of territory, may well seize power again in Kabul.

Elements in the Pakistani security establishment see the Taleban as a foil against India, which backs the current government in Kabul.

The US pays Pakistan for, among other things, the use of its territory and facilities and air space in pursuit of its military operations in Afghanistan.

The Trump administration, with its focus on getting more for its money abroad, may be taking a harder line than its predecessors.

"Pakistan has played a double game for years," Ms Nikki Haley, the US Ambassador to the United Nations, said on Tuesday. "They work with us at times, and they also harbour the terrorists that attack our troops in Afghanistan. That game is not acceptable to this administration."

On Wednesday, Pakistan's UN Ambassador, Ms Maleeha Lodhi, rejected the accusations.

Dr Fair told The Straits Times that a bigger question was whether the US had thought through what it would do if Pakistan cut off ground and air access for US supplies to Afghan government forces.