DAMASCUS, Syria — Sporadic violence persisted in Aleppo Wednesday as U.S. officials announced an agreement had been reached with Russia to extend Syria’s fragile cease-fire to the deeply contested northern city. The Syrian military said the truce would last only 48 hours.

Restoration of a partial truce would bring relief to residents on both sides of Syria’s largest city after two weeks of relentless violence that has killed nearly 300 people, destroyed hospitals and brought it to the brink of humanitarian disaster.

It was not immediately clear whether the new effort will be observed or for how long. The U.S. and Russia finalized a nationwide cease-fire in late February, but have struggled to make it stick.

The agreement was reached late Tuesday and took effect early Wednesday morning, Secretary of State John Kerry said.

Since the truce began, “we have seen an overall decrease in violence ... even though there are some reports of continued fighting in some locations, which does not surprise us because it only went into effect one minute after midnight,” Kerry said.

“We expect all the parties ... to fully abide by the renewed cessation in Aleppo. That means the regime and the opposition alike,” he told reporters. “We look to Russia ... to press for the regime’s compliance with this effort and the United States will do its part with respect to the opposition.”

The U.S. and Russia have been working to salvage the cease-fire they brokered together, which held surprisingly well until two weeks ago amid an alarming uptick of violence around Aleppo. Shells slammed into hospitals and residential areas on both sides of the divided city, plunging it into renewed violence that quickly escalated to levels unseen in months.

The agreement on Aleppo follows an earlier deal to reaffirm the truce in the Damascus suburbs and in coastal Latakia province.