US President Donald Trump's decision to freeze aid to Pakistan could affect almost two billion dollars' worth of assistance, a senior administration official said on Friday -- substantially more than first thought.

After an announcement designed to force Pakistan's military and intelligence apparatus to cut support for the Taliban and other Islamist groups, the official said that both US military assistance and Afghanistan coalition funding to Islamabad could be suspended.

It is "approximately two billion worth of equipment and coalition support funding that is in play," the official said on condition of anonymity.

After more than a decade of simmering US anger at links between Islamabad and the Taliban and the Haqqani network -- a Taliban affiliate -- President Donald Trump is trying to draw a line in the sand.

On the hook is almost $1 billion of US military equipment that has allowed Pakistan access to advanced military technology, but also funding that is meant to pay Pakistan for helping get US and NATO materiel into Afghanistan.

Analysts believe the United States is highly unlikely to freeze all that funding, which totals $1.9 billion, according to the source.

US officials have already indicated that there could be "exemptions" for programs deemed vital to US national security -- likely including cash for keeping Pakistan's nuclear weapons safe.

But nevertheless, the total figure of $1.9 billion is much higher than first indicated and is a signal of Washington's seriousness.

The senior administration official said "all options are on the table" when it comes to further moves, including stripping Pakistan of its status as a "major non-NATO ally" or calling in vital IMF loans.

The White House is demanding Pakistan crack down on Taliban elements and other groups that raise funds and take refuge in the border areas with Afghanistan.

It believes that a Pakistani crackdown could be pivotal in deciding the outcome of the war in Afghanistan -- entering its 17th year -- by weakening the Taliban militarily and forcing the organization to the negotiating table.

US officials believe that Pakistan's Inter-Services Intelligence agency and other military bodies have long helped fund and arm the Taliban for ideological reasons, but also to counter rising Indian influence in Afghanistan.

Islamabad denies those allegations and has called Trump's decision to threaten funding "counterproductive."

Pakistan's foreign ministry issued a cautious statement in which it said it was "engaged" with US officials and awaiting further details.

Without referring to the decision directly, it warned that "arbitrary deadlines, unilateral pronouncements and shifting goalposts are counterproductive in addressing common threats."

The announcement ignited some small protests in Pakistan on Friday, including in Chaman, one of the two main crossings on the border with Afghanistan where several hundred people gathered to chant anti-US slogans.

US officials admit that Pakistan could make life difficult for Washington by closing land routes that are vital to supply US troops in Afghanistan. But, the official said, it was "difficult but not impossible" to find other ways to get equipment in.