BRUSSELS — The United States won’t abandon its pursuit of peace in Syria after suspending direct U.S.-Russian talks on a cease-fire, U.S. Secretary of State John Kerry said today, even as he announced no new strategy to replace diplomatic efforts with Russia.

Washington and Moscow will still discuss Syria as part of larger multilateral negotiations, Kerry said, and they’ll make sure their warplanes conducting bombing missions in the Arab country don’t cross paths. Explaining Monday’s announcement to halt bilateral contacts over Syria, he said Russia has rejected diplomacy and chosen instead to help Syrian President Bashar Assad’s government achieve a military victory over rebel groups.

“We acknowledge in sorrow and, I have to tell you, a great sense of outrage that Russia has turned a blind eye to Assad’s deplorable use of these weapons of war, chlorine gas and barrel bombs, against his people,” Kerry said in a speech focused on trans-Atlantic ties at an event hosted by the German Marshall Fund in Brussels.

“Together, the Syrian regime and Russia seemed to have rejected diplomacy,” he said.”

Monday’s announcement dealt peace efforts a serious blow. Coupled with a Russian announcement to put on hold a plutonium disposal deal with the U.S., it showed chilly relations between the former Cold War foes turning even frostier.

Kerry said the decision wasn’t taken lightly.

“We are not giving up on the Syrian people. We are not abandoning the pursuit of peace,” the secretary of state said, with Washington maintaining its pursuit of a truce that grounds Russian and Syrian planes and allows aid to reach besieged, rebel-held areas of northern Syria.

The U.S. also will press on with military efforts against the Islamic State group, he said, and finding a durable political solution that allows Syrians to return home and alleviates Europe’s refugee crisis.

But of Russia and Syria’s airstrikes on the city of Aleppo, he said, “People who are serious about making peace behave differently.” The 5½-year war has killed as many as 500,000 people, chased millions of Syrians from their homes and allowed IS to carve out territory for itself and emerge as a global terror threat.

The Obama administration had been working with Russia for months to forge a cease-fire that ended Assad’s attacks on rebel and civilian areas and separated U.S.-supported, “moderate” groups from fighters linked to al-Qaida. Neither side proved able to fulfill its side of the bargain. But Washington has few other options, given President Barack Obama’s opposition to using military force against Assad’s military.

The White House and State Department said Monday there was no point to the bilateral discussions any longer because Russia hasn’t lived up to a Sept. 9 agreement that included a demand for unfettered humanitarian aid to places like Aleppo, which has been under Russian and Syrian bombardment.