MOSCOW — Russia and the United States announced on Tuesday that they would seek to convene an international conference within weeks aimed at ending the civil war in Syria, jointly intensifying their diplomatic pressure on the combatants to peacefully settle a conflict that has taken more than 70,000 lives and left millions displaced and desperate.

Secretary of State John Kerry and his Russian counterpart, Foreign Minister Sergey V. Lavrov, announced their agreement to arrange the conference after a day of intense diplomatic meetings here. Mr. Kerry, who was visiting Russia seeking to find common ground on the Syria conflict, told reporters at a joint appearance with Mr. Lavrov in Moscow that the aim would be to push the government of President Bashar al-Assad and the Syrian opposition to attend.

The announcement appeared to signal a strong desire by both countries to halt what has been a dangerous escalation in the conflict, with evidence of chemical weapons use, a surge in the number of civilians fleeing combat and a refugee crisis that is overwhelming Syria’s neighbors. Israeli aerial attacks this past weekend on suspected munitions sites in Syria heightened and further complicated the tensions in the region.

Mr. Kerry’s visit also came as the Obama administration faced increasing calls to intervene in the conflict with lethal military aid to the insurgency or perhaps stronger action like the enforcement of a no-fly zone over Syria to protect rebel-held areas. The effort to seek a negotiated solution with the Russians suggested that the administration wanted to first make a public push toward diplomacy.