In the strongest American suggestions yet that Russia is providing arms to the Taliban, the leader of U.S. and international forces in Afghanistan, Gen. John Nicholson, refused to refute reports that Moscow has provided the terrorist group with accelerated funding and weapons in the last year and a half, The Independent reported on Tuesday.

Nicholson made the comments to reporters in Kabul during Jim Mattis's first trip to the country as U.S. defense secretary, although he did not provide further details.

When a reporter asked Nicholson, "So you are not refuting that they are sending weapons?"

Nicholson replied: "Oh, no, I am not refuting that," CBS News reported.

Russia, which has long criticized the American handling of the war in Afghanistan, says it has diplomatic ties with Taliban officials to encourage peace talks with the Afghan government and to maintain security, but denies providing the Taliban with any weapons or financial aid, according to The Independent

Referring to a large Taliban attack last week on a military base in Balkh province that killed more than 140 Afghan troops, Nicholson said that "anyone who arms belligerents who perpetuate attacks like the one we saw" isn't focused on "the best way forward to a peaceful reconciliation."

Mattis added during his visit to Afghanistan that, "We'll engage with Russia diplomatically… We'll do so where we can, but we're going to have to confront Russia where what they're doing is contrary to international law or denying the sovereignty of other countries."

The Taliban, which ruled Afghanistan until the U.S. invasion in 2001, now controls about 40 percent of the country, according to CBS. The U.S. has almost 10,000 soldiers in Afghanistan, mainly to support Afghan security forces.