US Secretary of Defense Jim Mattis said that if reports that Russia was funnelling weapons into Afghanistan were confirmed, the country would be confronted on the breach of international law.
He was speaking in Kabul where he was initially expected to talk to troops with commanders and craft a new US strategy for the country; instead, his visit came three days after the Taliban attacked an Afghan army base, killing at least 170 people, in the deadliest assault on the military yet.
Mattis spoke at a joint news conference on Monday with the top American commander in Kabul, General John Nicholson, who said the US Army in Afghanistan continues to get reports of Russia assisting the Taliban with weapons.
The head of US and international forces in Afghanistan did not deny reports that Russia was providing support, including weapons, to the Taliban. When asked about reports that Russia was providing a range of help to the Taliban, that controls parts of Afghanistan, he replied: "Oh no, I'm not refuting that."
A senior US military official, speaking on condition of anonymity, told reporters that intelligence showed Russia was providing monetary and weapons support to the Taliban, including arms such as machine guns.
Mattis also said the Taliban needs to renounce violence and reject terrorism to join the political process. The US and Afghan leaders have made similar demands of the group before, but the Taliban has not made it to the negotiating table.
Afghanistan's top two defence officials resigned on Monday amid growing public pressure following Friday's deadly attack on the army base.
"Defence Minister Abdullah Habibi and Army Chief of Staff Qadam Shah Shahim stepped down with immediate effect," the office of Afghan President Ashraf Ghani announced on Twitter.
Shah Hussain Murtazawi, acting spokesman for Ghani, confirmed the resignations were because of Friday's attack.
TRT World spoke with journalist Bilal Sarwary who has more on the story.
An inside job?
Ghani's office also announced that he had replaced the commanders of four army corps in response to the attack, and defence officials said as many as eight army personnel had been arrested – heightening suspicions the attackers had inside help.
The attack underlines the scale of the challenge facing the Western-backed government and its international partners more than 15 years after the United States invaded the country.
At a news conference on Monday, Habibi and Shahim insisted their resignations were voluntary.
As many as 10 Taliban fighters, dressed in Afghan army uniforms and driving military vehicles, made their way onto an army base and opened fire on soldiers and new recruits eating a meal and leaving a mosque after Friday prayers, according to officials.
Officials told TRT World that the death toll from the assault has climbed to 170.
A senior US official said, based on intelligence and the types of tactics used, the Taliban-linked Haqqani network likely played a role.
"This is very typical Haqqani network tactics, techniques and procedures," said the official, adding that the United States believed it took four to six months to plan the attack.