A majority of US military veterans say the nearly 18-year war in Afghanistan was "not worth fighting," according to poll results released Wednesday.

The survey results come as the US and the Taliban engage in talks on bringing to a close the conflict which Washington launched in the wake of the September 11, 2001 attacks on the US.

"Majorities of both veterans [58 percent] and the public [59 percent] say the war in ­Afghanistan was not worth fighting. About four in 10 or fewer say it was worth fighting," according to the Pew Research Center.

The same held for the war in Iraq and the US military intervention against the Islamic State group in Syria, with 64 percent of veterans saying the former was "not worth fighting," and 55 percent saying the latter was "not worth it."

"Veterans who served in either Iraq or Afghanistan are no more supportive of those engagements than those who did not serve in these wars. And views do not differ based on rank or combat experience," the Pew Research Center said.

The polling had a margin of error of 3.9 percent for veterans and 3.1 percent for members of the general public.

Washington has said it wants to seal a political deal with the Taliban, ahead of Afghan presidential polls due in September, to allow foreign forces to begin to withdraw.

The US held six days of talks in Qatar with the Taliban which ran until Saturday.

Those discussions paused for Sunday and Monday's Afghan summit, which saw around 70 delegates including the Taliban discuss the future of the country.