Washington highlighted the economic potential of a peaceful Afghanistan in talks with the Taliban on Friday as it encouraged the start of talks between warring parties in the conflict-torn country.

Washington's special envoy for Afghanistan Zalmay Khalilzad tweeted that in a meeting with the militant group's political office in Doha, "we underscored the economic development opportunities that will follow a sustainable peace". 

"We agreed developing plans in support of peace can never start too early, assuming the two sides can overcome final hurdles on the path to intra-Afghan negotiations," he wrote.

The US and the Taliban have this week been thrashing out concerns over their deal inked in February, including intra-Afghan talks between militants and Kabul, and the release of 5,000 imprisoned insurgents.

A Taliban spokesman said in a statement its negotiators held talks with Adam Boehler, the chief executive of the US International Development Finance Corporation, on Afghanistan's "financial growth, reconstruction and development".

In February Washington pledged to withdraw its troops from Afghanistan by mid-2021 in return for security guarantees in a bid to pave the way for negotiations between the warring sides.

Under the landmark agreement, which excluded the Afghan government, Washington and the militants also said they would refrain from attacking each other.

"The Taliban recognise all Afghans will have to make compromises in order to draw in the required investment in Afghanistan's future," Khalilzad added.

The latest talks came as pressure mounted on US President Donald Trump over reports Russia's intelligence service offered Taliban militants bounties to kill American soldiers in Afghanistan.

House Speaker Nancy Pelosi on Thursday called for US sanctions against Moscow's spies over the allegations.

The top Democrat in Congress also said the White House had opposed sanctions "that pertained to the intelligence and the defence sectors" of Russia in previous bipartisan legislation that was aimed at punishing Moscow.

The Taliban have denied that their fighters received any Russian bounties, and the group's Qatar-based chief negotiator Mullah Abdul Ghani Baradar reiterated their pledge not to strike the US earlier this week.

Violence had dropped across much of the country after a brief Taliban ceasefire to mark the Islamic Eid al-Fitr festival in May, but officials say insurgents have stepped up attacks in recent weeks.

Most attacks by the Taliban have targeted Afghan security forces, although there are regular police reports that civilians have been killed in roadside bombings.