Zalmay Khalilzad will head to Afghanistan as well as neighboring Pakistan during the trip that began Monday and is scheduled to run through April 10.

The State Department did not confirm he would hold fresh talks with the Taliban but said he would stop in Qatar, the usual location for negotiations with the militants.

Khalilzad's trip is "part of an overall effort to facilitate a peace process that brings all Afghan parties together in inclusive intra-Afghan negotiations," the State Department said.

The emphasis on negotiations among Afghans comes as the Taliban refuse to sit down for talks with the internationally recognized government of President Ashraf Ghani, despite US appeals.

Tensions over the issue recently led to Ghani's national security adviser telling reporters in Washington that Khalilzad had not been transparent and accusing the US envoy, who was born in Afghanistan, of harboring personal ambitions in his native country.

As Khalilzad headed back, the US ambassador to Kabul, John Bass, also emphasized the role of Afghans.

"Afghans deserve to make their own choices about peace, including where they are prepared to compromise, where they are not prepared to compromise, & how to mend differences," Bass tweeted.

The last negotiations between Khalilzad and the Taliban closed on March 12 in Doha and appeared to make headway.

An outline of a deal is expected to see the United States withdrawing from Afghanistan in return for the Taliban promising not to let the country be used by foreign extremists -- the reason for the US attack following the September 11, 2001 attacks.

President Donald Trump has voiced impatience with continuing America's longest war and late last year ordered the withdrawal of half the 14,000-strong US troop contingent.

The State Department said Khalilzad would also visit Belgium, Britain, Jordan and Uzbekistan as he seeks global support for a peace deal.

He met last week in Washington with representatives from China, Russia and the European Union.