US House of Representatives Speaker Nancy Pelosi and other senior members of Congress made an unannounced visit to Afghanistan on Sunday, her office said.

Pelosi, who travelled to Afghanistan after a stop in Jordan on Saturday, met President Ashraf Ghani and visiting US Defence Secretary Mark Esper as well as top US military commanders and some of their troops, according to a statement released after the conclusion of the visit by the bipartisan delegation.

The lawmakers' trip to the Middle East and South Asia occurred amid questions about the United States' commitment to its allies after President Donald Trump's sudden withdrawal of US troops from northeastern Syria over his long-time desire to unwind from foreign military engagements. Pelosi's relations with Trump are at a low point as she leads an impeachment inquiry against him.

Trump last month broke off negotiations with Afghan Taliban militants aimed at ending the United States' longest war, a move that critics say highlighted a confused US approach to Afghanistan.

The congressional visit coincided with one by Esper, who told reporters "the aim is to still get a peace agreement at some point, a political agreement".

Pelosi said her delegation was briefed by US diplomats on reconciliation efforts with the Taliban and also met Afghan Chief Executive Abdullah Abdullah and civil society leaders, including Afghan women.

She said in a statement that they also "heard more about the still-pending status of results from the Afghanistan presidential election in September, which we all hope will be available soon".

Preliminary results from the September 28 election have been delayed past their Oct 19 release, for at least a week, Reuters reported on Oct 17.

"Our delegation emphasised the central importance of combating the corruption which endangers security and undermines the Afghan people's ability achieve a stable and prosperous future," Pelosi said.

"We underscored that the women of Afghanistan must be at the table for reconciliation talks."

Trump halted talks with the Taliban, aimed at striking a deal for US and other foreign troops to withdraw in exchange for Taliban security guarantees, after it carried out a bomb attack in Kabul last month that killed 12 people, including a US soldier.

The United States says it has increased the pace of operations against militants in Afghanistan since Trump walked away from talks with the Taliban.