The United States warned Russia on Friday that potential military cooperation envisioned by a cease-fire deal in Syria will not happen unless humanitarian aid begins to flow into Aleppo and other besieged communities. The warning came as President Barack Obama's top national security aides continued to wrangle over whether and how to cooperate militarily with the Russians in the event those conditions are met.

Secretary of State John Kerry told Russian Foreign Minister Sergey Lavrov in a telephone call that Moscow must persuade the Syrian government to get the aid moving or a joint facility to coordinate attacks on extremist groups and share intelligence will not be set up, the State Department said. Kerry called the delays in assistance to Aleppo "repeated" and "unacceptable" and said Russia must press Syrian President Bashar Assad to allow deliveries.

Kerry "emphasized that the United States expects Russia to use its influence on the Assad regime to allow UN humanitarian convoys to reach Aleppo and other areas in need," State Department spokesman John Kirby said. "The secretary made clear that the United States will not establish the Joint Implementation Center with Russia unless and until the agreed terms for humanitarian access are met."

The agreement that Kerry and Lavrov reached last week calls for sustained delivery of humanitarian aid, along with a decrease in violence, as a requirement for the military cooperation to target Islamic State and al-Qaida-linked groups. The arrangements are very detailed on the mechanics of ending violence in Aleppo and opening up a key artery to the city for humanitarian deliveries. The agreement has not been made public but officials familiar with it have told The Associated Press it contains a highly technical series of requirements for both Assad's government and opposition forces.

These include precise calculations, in meters, on how the sides would pull back from a key artery into Aleppo and where they would have to redeploy weaponry. A main focus is on ensuring rapid, safe, unhindered and sustained humanitarian access to all people in need.

The Russian Foreign Ministry's description of the Kerry-Lavrov call said the two men had focused on implementation of the agreement that they reached a week ago in Geneva, according to Russian news agencies.

The ministry said Lavrov had once again called for the United States to make the agreement public and have the United Nations Security Council endorse it. He also restated Moscow's demand that the U.S. use its influence with opposition forces it supports to distance themselves from al-Qaida-linked fighters.

Meanwhile, a senior Russian military official said Moscow would help ensure the cease-fire in Syria for another three days, but warned the United States to press the rebels to end violations of the truce.

Lt. Gen. Viktor Poznikhir of the Russian military's General Staff declared readiness to extend the U.S.-Russia-brokered cease-fire for another 72 hours, adding that Moscow expects Washington to take "resolute action" to end violations by the U.S.-backed opposition units. He said the Syrian army has fully complied with the truce that went into force Monday, while the opposition units have violated it 144 times since then.

The Sept. 9 agreement also sets out a broad outline of how the military cooperation facility would be set up if violence is reduced and aid delivered over the course of seven continuous days.

The Pentagon, however, has serious reservations about coordinating air strikes and sharing intelligence with Russia and has raised objections on numerous grounds, according to U.S. officials.

White House spokesman Josh Earnest downplayed the significance of divisions between the State and Defense departments on the wisdom of deepening military cooperation with Russia. But he confirmed that Obama planned to meet later Friday to discuss the cease-fire agreement and the broader campaign against the Islamic State group with his top national security advisers, including Kerry and Defense Secretary Ash Carter. The White House said the meeting was scheduled before the cease-fire deal was announced.

"The president didn't staff his national security team with 'yes' men and 'yes' women ... the president expects to receive advice based on their differing perspectives" and expertise, Earnest said. Earnest added that once Obama has made a decision, he expects his team to execute that strategy. "The president has no doubt that will happen," he said.


Bradley Klapper and Kathleen Hennessey contributed to this report.