KABUL, Afghanistan — The top American commander in Afghanistan sought to reassure Afghan forces on Thursday that they still had the full backing of the United States, after a report that the support was being dialed back in preparation for an imminent peace deal with the Taliban.

The fighting in Afghanistan has intensified as United States diplomats and the insurgents have worked through eight rounds of negotiations in Qatar. Afghan forces and the Taliban have both sought to increase their political leverage through violence, with both sides suffering heavy casualties and civilians bearing the brunt of the attacks.

But on Monday, Newsweek magazine, citing anonymous sources in Washington, said that United States personnel had been ordered to limit offensive operations against the Taliban and to stop advising Afghan forces.

Gen. Austin S. Miller, who leads the American and NATO missions in Afghanistan, brushed aside such reports as “false.”