The top US commander for the Middle East painted a grim picture on Tuesday of the peace process with the Taliban in Afghanistan, saying the current level of attacks is higher than allowed in the plan and he has no confidence the group will honour its commitments.

Marine Gen Frank McKenzie told the House Armed Services Committee that he has plans to cut the number of troops to 8,600 by the summer, but so far the US “has not developed military plans” for the full withdrawal in 14 months that is called for in the peace plan signed 29 February.

“To date, Taliban attacks are higher than we believe are consistent with an idea to actually carry out this plan,” Gen McKenzie said. “If they're unable to draw down the current level of attacks, then the political leadership will be able to make decisions based on that.”

He added that his optimism or pessimism about the future doesn't matter because any decisions will be based on facts and what happens on the ground.

Both Gen McKenzie and Kathryn Wheelbarger, a top Pentagon policy adviser on international affairs, said America's complete troop withdrawal is contingent on whether the level of violence is reduced and the Taliban adheres to its commitments.

Gen McKenzie said he would recommend against that full pullout if attacks continue and the Afghan forces can't protect their own country without direct US support. Ms Wheelbarger called the full pullout “aspirational” and said Defense Secretary Mark Esper would reassess the matter if the Taliban doesn't abide by the agreement.

The United States has begun withdrawing troops from Afghanistan, taking a step forward on its peace deal with the Taliban. And Afghan President Ashraf Ghani promised on Monday to start releasing Taliban prisoners, but by Tuesday he had not issued a decree to free them.

The US-Taliban deal was touted as Washington's effort to end 18 years of war in Afghanistan. The next crucial step was to be intra-Afghan talks in which all factions including the Taliban would negotiate a road map for their country's future.

That plan has been thrown into chaos because both Mr Ghani and his main political rival, Abdullah Abdullah were each sworn in as president in separate ceremonies Monday. Mr Abdallah and the elections complaints commission had charged fraud in last year's vote.

Mr Ghani, however, said Tuesday that he'd start putting together a negotiating team, and he said he would announce a decree to free the prisoners. His comments on the prisoner release came after the US and a number of foreign dignitaries appeared to back his claim to the presidency by sending their representatives to his inauguration.

Mr Esper last week said “the entire process will be conditions-based, and we will retain in Afghanistan the necessary capabilities to protect our service members and allies and support the Afghan security forces.”

A key challenge will be whether al-Qaida is able to resurge in Afghanistan and present a threat once again to the US

Gen McKenzie was asked what evidence the US has that the Taliban have cut ties with al-Qaida.

He said it's pretty clear the Taliban are actively fighting the Islamic State affiliate in Afghanistan, but added that he is “less optimistic” about al-Qaida.

“That's something they (the Taliban) are going to have to demonstrate that has not yet been demonstrated,” he added, referring to the Taliban showing that it has severed ties to the extremist group that planned the Sept. 11, 2001 attacks from Afghanistan. He said the US will have “ample time to see if they actually do that” before the US completes a troop withdrawal.

He said the key threats to the US continue to be the ability of al-Qaida and the Islamic State to generate attacks against the US.