President Donald Trump on Friday said the Taliban could "possibly" overrun the Afghan government after the United States withdraws from the country, leaving the US-backed authorities to fend for themselves.

"Countries have to take care of themselves," Trump told reporters at the White House. "You can only hold someone's hand for so long."

Asked if the Taliban could eventually seize power, Trump said it's "not supposed to happen that way but it possibly will."

"We can't be there for the next 20 years. We've been there for 20 years and we've been protecting the country but we can't be there for the next -- eventually they're going to have to protect themselves," he said.

Trump said the Afghan government's ability to defend itself from the guerrillas after US forces pull out was unknown.

"I don't know. I can't answer that question," he said. "We'll have to see what happens."

On February 29, the United States and the Afghan Taliban signed a peace deal in Qatar after a long spell of negotiations.

 Taliban deputy leader Mullah Abdul Ghani Baradar and US envoy Zalmay Khalilzad inked the deal in an opulent hall in a five-star hotel in Dohar, Qatar.

Foreign Minister of Pakistan, which is believed to have played a key role in the deal, attended the ceremony on special invitation.