The Taliban is not living up to commitments made under an agreement with the US earlier this year, Defence Secretary Mark Esper said on Tuesday,
The statement comes amid fears that the fragile deal could crumble because of a political deadlock in Kabul and increasing violence elsewhere.
After lengthy talks behind closed doors, the Taliban and Washington signed an agreement in February to halt violence and move towards talks with the Afghan government, but attacks by the group have since increased.
"I don't think they are," Mr Esper told reporters when asked if the Taliban were living up to their commitment.
He said the Afghan government was also not living up to its commitment. The Afghan government was not part of an agreement between the United States and the Taliban.
Mr Esper said the Afghan government and the Taliban "both need to come together and make progress on the terms that [are] laid out".
Progress on moving to negotiations between the militant group and the Afghan government has been delayed, in part by the political feud between President Ashraf Ghani and his rival Abdullah Abdullah. The two claim to be Afghanistan's rightful leader following September's disputed election. Both sides claim to be close to a reconciliation but as yet no official progress has been made to solve the crisis.
The political deadlock comes as the Taliban has increased the pace of violence.
The Taliban have launched more than 4,500 attacks in Afghanistan in the 45 days since signing a deal with the United States that paves the way for a US troop drawdown, according to data seen by Reuters.
The US is continuing its drawdown of forces in Afghanistan, which are expected to reach about 8,600 troops this summer.
Senior western, Afghan and independent officials tracking the ground situation say the increase in attacks shows the insurgent group's wilful disregard of a pledge to reduce violence made as part of the accord signed in late February.
The violence in the war-damaged nation has coincided with the rapid spread of the coronavirus infection.