US President Joe Biden has said it will be tough to meet the May 1 troop withdrawal deadline but that he has not yet made the decision as to when troops will leave.

In an interview with ABC news on Wednesday night, Biden said he is still reviewing the agreement sealed between his predecessor Donaly Trump and the Taliban in February last year.

“I’m in the process of making that decision now as to when they’ll leave,” Biden said.

“The fact is that, that was not a very solidly negotiated deal that the president – the former president – worked out. And so we’re in consultation with our allies as well as the government, and that decision’s going to be – it’s in process now.”

Biden said it would be “tough” for all service members to leave by May 1.

“It could happen,” he said, “but it is tough.”

Currently Washington official reports there are 2,500 US troops in the country but last week New York Times reported there are at least 3,500 US soldiers in Afghanistan.

That’s 1,000 more than Washington has disclosed.

The NYT reported the “cloudy accounting” around troops numbers results from some Special Forces units having been put “off the books”.

According to a senior US official, the presence of some temporary and transitioning units also accounted for the additional troops.

A second official told NYT that these troops include Joint Special Operations Command units, some of them elite Army Rangers, who work under both the Pentagon and the CIA while deployed to Afghanistan.

Having more troops in a country than the Defense Department officially acknowledges is common practice, NYT reported.

According to the report, the United States often details military troops to the CIA or other agencies, declares that information “classified” and refuses to publicly acknowledge their presence.