Russian President Vladimir Putin attends a meeting with U.S. Secretary of State John Kerry at the Kremlin in Moscow, Russia, July 14, 2016. (Sputnik/Reuters)

Secretary of State John F. Kerry, carrying a new U.S. proposal for coordinated U.S.-Russia counterterrorism operations in Syria, met with President Vladimir Putin here Thursday night in the latest Obama administration effort to salvage a failing cease-fire and revive suspended peace negotiations in the Syrian civil war.

Kerry’s motorcade went directly from the airport to the Kremlin, a sign of the urgency he places on testing Moscow’s intention to abide by its commitments in Syria.

Putin, speaking at Kerry’s side before the closed-door talks, said a telephone conversation last week with President Obama had “convinced” him “that it’s our sincere desire . . . to yield tangible results.”

“I hope after today’s consultations, you’ll be able to advise [Obama] of the progress made and possible headway for us to make,” Putin told Kerry. The meeting ended after three hours.

Kerry, a State Department statement said, “expressed concern” to Putin about Syria’s “repeated violations” of the cease-fire, and the leaders discussed the need to “increase pressure” on terrorist groups there. The statement said Kerry emphasized that “absent concrete, near-term steps, diplomatic efforts could not continue indefinitely,” and that discussions would continue Friday with Foreign Minister Sergei Lavrov.

Senior State Department officials said before the meeting that Kerry was not optimistic that the trip — his third here in the past 12 months — would produce a breakthrough. “At present, we are not conducting or coordinating military operations with Russia, nor is it clear we will reach an agreement to do so,” one official said.

In Geneva, senior United Nations officials expressed support for the controversial proposal, which is designed to “integrate” U.S. and Russian air operations against terrorist targets, while stopping attacks against civilians and moderate opposition forces by Syrian and Russian aircraft.

“I hope there is clearly some kind of general understanding and progress on it,” U.N. special envoy Staffan de Mistura said. He voiced hope that the proposal — which would delineate moderate opposition positions from those of al-Qaeda-linked Jabhat al-Nusra — would resolve what he called “non-constructive ambiguity” about the extremist group’s locations.

Russian and Syrian bombing of what they say are joint positions has been “one of the main problems for sustainability of the cessation of hostilities,” de Mistura said, referring to a U.S.-Russian sponsored cease-fire agreed to in February. The opposition is a party to the truce; Jabhat al-Nusra and the Islamic State are not.

Failure of the cease-fire, and the Syrian government’s refusal to allow humanitarian aid into besieged areas where hundreds of thousands of civilians lack food or medical care, led to a suspension of political negotiations over an end to Syria’s civil war.

“Barrel bombing and aerial bombing of civilian areas,” de Mistura said, “cannot continue if we are to have serious, constructive talks.” The U.S. proposal would require Russia to use its leverage to ground the air force of its Syrian ally and restrict its own strikes to agreed terrorist locations.

Kerry declined to comment on the proposed U.S.-Russian Joint Implementation Group, the terms of which were first reported by The Washington Post. “We’ll have plenty of time to talk about it” after the meeting with Putin, he told reporters in Paris before flying to Moscow.

Kerry has expressed frustration that what he thought were common understandings with Moscow have not produced the desired outcome. Instead, Russian assistance to Syrian President Bashar al-Assad has helped restore Assad’s ability to go on the offensive against the opposition and shrug off demands for political change.

“The reality is the Syrian regime has violated every commitment it has made — or that Russia has made on its behalf — and has squandered every opportunity to build confidence with the Syrian people,” the State Department official said, speaking on the condition of anonymity because the U.S. proposal to Russia has not been finalized. “In the meantime, the Assad regime continues to destroy its own country and people in order to cling to power.”

Officials said repeatedly that U.S. patience is running thin.

“We will not commit indefinitely to diplomacy that does not achieve real results,” one insisted. “We cannot provide political cover for those seeking to pursue a different agenda. . . . It’s long past time that Russia decides whether it is serious about advancing such shared objectives in Syria.”

The proposal Kerry is discussing with Putin and Lavrov would expand U.S. targeting in Syria to include Jabhat al-Nusra as well as the Islamic State, which is only tangentially involved in the civil war against Assad. Jabhat al-Nusra is a direct party to the conflict against the government, operating primarily in the same areas of northwestern Idlib and Aleppo provinces as U.S.-backed opposition ­forces.

U.S. jets, to avoid involvement in the civil conflict and for legal reasons, have targeted Jabhat al-Nusra only a few times since the United States began bombing in Syria in September 2014.

A U.S. document outlining what it called an “Approach for Practical Russian-American Cooperation” against the Islamic State and Jabhat al-Nusra and a strengthening of the truce indicated that the Joint Implementation Group, headquartered in Amman, Jordan, would include U.S. and Russian military officials, at the level of colonel, and equally senior intelligence. Its first task, to be completed within five days, would be to map locations of “concentrated” Jabhat al-Nusra presence and those areas where opposition forces are concentrated with little or no Jabhat al-Nusra presence.

Sharing intelligence, members of the Joint Implementation Group would jointly identify “actionable” Jabhat al-Nusra targets, including leadership, training camps, logistical depots, supply lines and headquarters, and designate them for airstrikes by either Russian or U.S. forces. Other areas would be off limits to both.

Once an initial set of targets is agreed upon and all combat air activities by Syria have ceased, coordinated U.S.-Russian airstrikes would begin.

The plan sets July 31 as a target date for implementing the joint counterterrorism plan, establishment of a durable, nationwide cease-fire, and making progress toward a political transition in Syria. De Mistura has said he hopes to restart the talks by Aug. 1.

A separate document describing terms of reference for the JIG describes it as a “liaison body” designed “to expose portions of a participant’s targeting and airstrike planning functions to the other participant. The United States and Russia,” it says, “should inform one another through the JIG of final plans for operations against a mutually selected target no later than the day before execution.”

Information to be exchanged includes “the general time of the strike, the intended method of target attack, general force composition, routing of the strike and precise details of the target being struck,” and commitment to “ensuring that the intended actions are deconflicted by time and/or geography” and will not be targeted by either side’s air defenses or that of the Syrian “regime.”

A number of U.S. military and intelligence officials, as well as outside experts, have expressed concern about the proposal, saying that it would reward Russia for its violation of earlier agreements and help solidify Assad’s position.

Kremlin spokesman Dmitry Peskov said he would not comment on the U.S. offer before Moscow sees what the Obama administration is proposing.

But there is a widespread sense that time is running out on a solution to the protracted Syrian conflict, which the administration has said is detracting from its efforts against the Islamic State.

In describing the humanitarian situation, U.N. envoy Jan Egeland said that “one-third of the war wounded are women and children. It’s not fighters, it’s women and children, and they are bleeding to death because they cannot be evacuated, or dying because there are no medical personnel, or dying because they are attacked in their beds. This is how low it has sunk in Syria.”

DeYoung reported from Washington.