WASHINGTON: US President Joe Biden has said that it would be "tough" to meet the deadline to withdraw American troops from Afghanistan by May 1, as agreed with the Taliban in a deal secured under Donald Trump.

The Taliban insurgents have largely stuck to a promise not to attack US or other foreign troops since the agreement was struck in February last year, but they say the date to end America's longest war is inflexible.

"Could happen, but it is tough," Biden said when asked about the May 1 deadline in a TV interview broadcast on Wednesday. "I'm in the process of making that decision now."

The Taliban quickly reacted to Biden's comments, with a spokesman telling AFP there would be "consequences" if the United States did not stick to the agreed timetable -- further raising pressure on the fragile peace process.

Biden also took a direct swipe at Trump's Afghanistan policy, saying it "was not a very solidly negotiated deal" that the then-president oversaw.

"The failure to have an orderly transition from the Trump presidency to my presidency... has cost me time and consequences. That's one of the issues we're talking about now, in terms of Afghanistan," he added.

The United States is supposed to pull out all its troops by May 1 in an agreement that saw the Taliban agree to peace talks with the Afghan administration of President Ashraf Ghani.