WASHINGTON - The US team that tried for more than a month to negotiate a reopening of blocked Pakistani supply routes into Afghanistan is coming home without an agreement, US officials said Monday.

Both sides indicated they remain open to making a deal, but the departure of the negotiators appeared to signal that the Americans see little prospect of a breakthrough any time soon. Adding to the appearance of an impasse was the Pakistanis’ refusal to grant a visiting Pentagon official a meeting with their top general.

White House press secretary Jay Carney put the onus on Pakistan to resume serious talks.

“We saw it as the right move to withdraw’’ the US negotiating team, he said, adding that it had largely completed its work. “We are ready to send officials back to Islamabad when the Pakistani government is ready to conclude the agreement.’’

Carney said several issues remain unresolved, but he gave no details.

The disagreement over the supply routes is one of numerous tensions in the US-Pakistani relationship. In recent days the Americans have emphasized their frustration at Pakistan’s refusal to do more to stop Pakistani-based insurgent groups from crossing into Afghanistan to fight NATO and Afghan troops.

Officials in Washington and Islamabad would not detail what led to the break in the supply route talks.

However, two senior US officials familiar with the negotiations said the Pakistanis were holding out for an apology for the deaths last November of 24 Pakistani soldiers in a US airstrike, which was what triggered Pakistan to close the border.

The United States, which says the airstrike was called in by a US-Afghan team, has said it regrets the deaths but insists it will not apologize.

The border crossings had been an important means of getting US war materiel into Afghanistan. Since then, NATO and the United States have been using a circuitous, more costly northern route to bring supplies to the war front.