U.S. Marine General Kenneth McKenzie, who oversees American troops in the region, declined to comment on the diplomatic negotiations themselves.
But the remarks represent the latest sign of how a wave of Taliban violence has cast a long shadow over a draft peace deal struck between U.S. and Taliban negotiators this week that could lead to a drawdown in U.S. troops from America's longest war.
"It is particularly unhelpful at this moment in Afghanistan's history for the Taliban to ramp up violence," McKenzie, head of U.S. Central Command, told reporters traveling with him.
Taliban fighters, who now control more territory than at any time since 2001, launched fresh assaults on the northern cities of Kunduz and Pul-e Khumri over the past week and carried out two major suicide bombings in the capital Kabul.
One of the blasts took the life of U.S. Army Sergeant 1st Class Elis A. Barreto Ortiz, 34, from Puerto Rico, bringing the number of American troops killed in Afghanistan this year to 16.
McKenzie said that, for the peace process to move forward, "all parties should be committed to an eventual political settlement" which, in turn, should result in reduced violence, he added.
"If we can't get that going in, then it is difficult to see the parties are going to be able to carry out the terms of the agreement, whatever they might or might not be," McKenzie said.
Under the draft accord, thousands of U.S. troops would be withdrawn over the coming months in exchange for guarantees that Afghanistan would not be used as a base for militant attacks on the United States and its allies.
However, a full peace agreement to end more than 18 years of war would depend on subsequent "intra Afghan" talks. The Taliban have rejected calls for a ceasefire and instead stepped up operations across the country.
NEW CIVIL WAR?
For Afghans, the Taliban's recent escalation of attacks has underscored fears that it may be impossible to reach a stable settlement following any complete U.S. withdrawal.
Many have worried about a fracture along ethnic and regional lines, with Persian-speaking Tajiks and Hazaras from the north and west against southern and eastern Pashtuns, the group that have supplied most of Afghanistan's rulers and where the Taliban draw most support. Memories of the 1990s civil war are vivid.
Some Taliban are based in neighboring Pakistan, where McKenzie held talks on Saturday with a top Pakistani general. More talks are scheduled for Sunday.
McKenzie said he did not know whether any of the planning for the recent wave of attacks in Afghanistan came from Pakistan-based militants.
But McKenzie commended Pakistan for supporting the peace efforts in Afghanistan, in the latest sign of an improvement in long-fraught relations between Washington and Islamabad.
"A lot of Pakistanis have been killed by militant attacks inside Pakistan. I think Pakistan sees the benefits of a stable Afghanistan," McKenzie said.
"So I think they are committed to helping us get to a political solution in Afghanistan."
For years, the United States accused Pakistan of failing to do enough to combat militants based on its territory. Pakistan denies accusations that it supports the Taliban but many members live there.
McKenzie acknowledged there were militant safe havens in Pakistan but said: "I believe Pakistan operates against those safe havens.""I believe that work is incomplete but it is continuing," he added.