Marine Gen. Kenneth Frank McKenzie, head of U.S. Central Command, did not say what form of help the Taliban was given -- whether it was airstrikes, intelligence or simply a temporary cessation of U.S. attacks.
"There was very limited support from us, and I would characterize that as very limited support," he said.
In testimony before the House Armed Services Committee, McKenzie also did not say when or where the support was given to the insurgent group, whose stated goal for more than 18 years has been to drive the U.S. from Afghanistan.
However, McKenzie suggested that assistance to the Taliban may have come into play in remote areas of Afghanistan's southeastern Nangarhar province against the ISIS offshoot called Islamic State-Khorasan Province, or ISIS-K.
"Over the last several months in eastern Afghanistan, we've watched the Taliban compress and crush ISIS presence on the ground in southern Nangarhar province, and they've been very effective doing that," McKenzie said.
"It was a bloody mess, but they did it. In fact, ISIS really now no longer holds ground in Nangarhar province," McKenzie said."
At a later Pentagon briefing, Rear Adm. William Byrne, vice director of the Joint Staff, declined to comment on McKenzie's statements but said a main goal of U.S. policy was to rid Afghanistan of both ISIS and al-Qaida.
"I don't have any specifics to provide you [on McKenzie] but that's the hope, in that every force there is countering ISIS. Every force there is countering al-Qaida," Byrne said.
In his House testimony, McKenzie also expressed skepticism that the Taliban would keep their part of the bargain with the U.S. to allow for the reduction of U.S. forces in Afghanistan to 8,600 by this summer and a complete withdrawal over 14 months.
Under the deal between U.S. special envoy Zalmay Khalilzad and Taliban leaders in Doha, Qatar last month, a seven-day "reduction in violence" was agreed to and was to be followed by talks between the Taliban and the Kabul government on a final peace settlement.
However, McKenzie said that the Taliban were continuing attacks on Afghan forces in violation of the agreement with the U.S.
He said the U.S. troop reductions were conditions-based, and if the Taliban continue attacks, "my advice would be not to continue that reduction."