The United States rebuffed Friday an appeal by the Taliban to release Afghan assets frozen after their takeover, saying the new government in Kabul must "earn" legitimacy first.

Thomas West, the US Special Representative for Afghanistan, said in a tweeted statement that Washington had long made clear that if the Taliban claimed power by military force rather than negotiating with the previous US-backed government, that critical non-humanitarian aid would be cut off.

"That is what occurred," West said.

"Legitimacy & support must be earned by actions to address terrorism, establish an inclusive government, & respect the rights of minorities, women & girls -- including equal access to education & employment," he said.

In an open letter Wednesday the Taliban called on the US Congress to release Afghan assets frozen after their takeover of the country in August.

Washington seized nearly $9.5 billion in assets belonging to the Afghan central bank, and the aid-dependent economy has effectively collapsed -- with civil servants unpaid for months and the treasury unable to pay for imports.

Taliban Foreign Minister Amir Khan Muttaqi said in the letter that the biggest challenge facing Afghanistan was financial insecurity, and warned that economic turmoil at home could lead to trouble abroad.

West said that Afghanistan was already in dire economic and humanitarian straits before the Taliban takeover, due to years of war, drought and the Covid-19 pandemic.

"The US will continue to support the Afghan people with humanitarian aid," he said, saying $474 million has already been provided this year.

Washington is also "making every effort to help the UN & humanitarian actors scale up to meet needs this winter," he said.

"We will continue clear-eyed, candid diplomacy with the Taliban," he added.