The United States and Russia are working together to include Aleppo in a so-called “regime of silence”—a freeze in fighting, aimed at bolstering the broader truce.

U.S. Secretary of State John Kerry said Washington and Moscow have agreed to boost the number of Geneva-based truce monitors to track violations “24 hours a day, seven days a week.” He added the U.S. would press moderate rebels to separate themselves from Al-Nusra Front jihadists in Aleppo.

“The line that they’re trying to draw now would prohibit any kind of incursion into Aleppo. It will not allow Aleppo to fall. It will not allow this to be prosecuted and continued,” said Kerry.

“And very, very clearly, unequivocally, if Assad does not adhere to this, there will clearly be repercussions. And one of them may be the total destruction of the ceasefire and they go back to war. I don’t think that Russia wants that. I don’t think Assad is going to benefit from that.”

Meanwhile, Russian Foreign Minister Sergey Lavrov announced that a joint monitoring center will be operational within days in Geneva .

“We call for all members of the international society, especially the U.S. as the chair nation of the international support group for Syria, to exert influence on the members of the anti-terrorism coalition, so that those ultimatums and attempts of military solutions that aim to undermine the progress of peace talks will cease,” said Lavrov.