WASHINGTON (REUTERS, AFP) - President Donald Trump said he wants to pull US troops out of Afghanistan but is concerned that without an American military presence, the country could be used as a base for terrorist attacks on the United States.

In an interview on Fox News broadcast on Monday (July 1), Trump said the problem with pulling the 9,000 US troops from Afghanistan, the site of America's longest war, is that the country is a "lab for terrorists".

"I call it the Harvard of terrorists," Trump said.

He recounted conversations he had with US military officials telling them of his desire to remove troops. He said they warned him it would be better to fight terrorists in Afghanistan than at home.

"'Sir, I'd rather attack them over there, then attack them in our land,'" Trump said a general had told him. "It's something you always have to think about," Trump said.

Even if the United States did remove its troops, Trump said, it would leave a "very strong intelligence" presence in Afghanistan.

The interview with Trump was taped over the weekend, prior to Monday's truck bomb and gun attack by Taliban fighters that killed six people and wounded 105 in Kabul, including 50 children.

The White House condemned the attack.

"This brazen attack demonstrates the Taliban's callous disregard for their fellow Afghans, who have repeatedly voiced the urgency of finding a peaceful resolution to the conflict," the White House said in a statement.

US special peace envoy Zalmay Khalilzad held a seventh round of peace talks on Monday with the Taliban in Qatar, aimed at bringing the 18-year-old war to an end.

The focus of the peace talks has been a Taliban demand that foreign forces leave and a US demand for a guarantee that Afghanistan will not be used as a base for attacks elsewhere.

The United States went to war in Afghanistan in response to the Sept 11, 2001, attacks on New York and the Pentagon, seeking to oust the Taliban militants harbouring Saudi-born al Qaeda leader Osama bin Laden, who led plans to carry out the attacks. About 2,400 US forces have been killed in the conflict.