[WASHINGTON] President Barack Obama voiced "deep concern" that key elements of a Syria ceasefire are not being upheld Friday, after huddling with top national security aides.
A week after the United States and Russia agreed to halt bombing and let humanitarian aid into Aleppo, shaky implementation figured prominently in a National Security Council meeting scheduled to focus on the Islamic State group.
"The President expressed deep concern that, despite decreased violence across the country, the Syrian regime continues to block the flow of critical humanitarian aid," the White House said.
The deal has somewhat quieted the bombs over Syria's second city Aleppo, but aid convoys have not been allowed to reach the roughly 250,000 civilians besieged by government forces.
Mr Obama reportedly told aides that the next steps in the deal - closer military coordination with Russia - will require "seven continuous days of reduced violence and sustained humanitarian access." Any US military cooperation with the Kremlin could be seen as a tacit endorsement of its war in Syria and support for the Assad regime, which has used barrel bombs and chemical weapons against civilians.
Some within the Pentagon have expressed deep reservations about the agreement, brokered between Secretary of State John Kerry with his Russian counterpart Sergei Lavrov, forcing Mr Obama to referee disputes.
Russia, critics say, has repeatedly used talks to blunt criticism of its support of Mr Assad, sow doubt among US allies on the ground and buy time for Syrian forces to improve their position.
But White House and State Department officials have argued any ceasefire, even if imperfect and fleeting, offers desperately needed respite from a brutal five-year civil war that has killed 300,000 people.
Privately, they express concern that Russia may be stalling for time, but say ultimately talks are the only way the Syrian war will come to an end.
The Russian government, which controls the media and actively stifles political opposition, faces virtually no domestic pressure over its actions in Syria.
The UN Security Council on Friday canceled a planned meeting over disagreements between Russia and the United States over disclosing details of the ceasefire.
France and other US allies have publicly stated they want more details.
"Since we could not agree on an approach to briefing the council that would not compromise the operational security of the arrangement, the meeting was cancelled," a spokesman for the US mission said.