Such a partnership would undercut months of United States criticism of Russia's military intervention in Syria, and it would put the U.S. alongside Syrian president Bashar Assad's chief global backer, despite years of American demands for Assad to leave power.
Secretary of State John F. Kerry wrangled for hours with senior Russian officials in Moscow on Friday, discussing a plan that includes first-time coordination between the USA and Russia on airstrikes targeting militant groups operating in Syria.
He said this after talks with his Russian counterpart Kerry in Moscow. Regarding Nusra, he said, "nothing can justify terrorist attacks".
"I want to emphasize though that they are not based on trust".
"And you and I and your teams are in the enviable position of actually being able to do something about it", he added, addressing Lavrov.
Mr. Kerry described three hours of meetings with Mr. Putin on Thursday evening as "extremely frank and serious".
The United States is offering Russian Federation a new military pact against Islamic State and al Qaida in Syria, according to a leaked proposal.
In exchange for USA cooperation, the Russians would pressure Assad into ending a bombing campaign against moderate militant groups and civilians, and allow unfettered aid to besieged, rebel-held areas.
Kremlin spokesman Dmitry Peskov said yesterday that the talks between Putin and Kerry had not marked the start of cooperation "to significantly improve the effectiveness of efforts in the fight against terrorism".
U.S. officials were careful not to call the talks a last chance for diplomacy to resolve the bloody five-year-old conflict, but they warned time was running out. "Unfortunately, we've seen them devote too much of their attention to using their military might to prop up the Assad regime". "We have a difference with Russian Federation on that", Kerry said.
Meanwhile, there was no sign in Damascus that Assad feels under any pressure to agree to talks on a new government, the next stage in the process if a ceasefire is restored.
"Only the Syrian people define who's going to be the president, when to come, and when to go".
Commenting on relations between the two countries, Lavrov said that there is an understanding between Moscow and Washington that they need each other and are needed by the global community.
De Mistura said peace talks "have a target date of August" and need to be "a credible beginning of a roadmap towards a political transition".
A landmark partial ceasefire they brokered in February - which did not include Islamic State or Al-Nusra - has since all but collapsed amid continued heavy fighting.
The Washington Post newspaper had reported that Kerry was bringing with him to Moscow a proposal for intelligence sharing with Russian Federation over Syria and joint selection of bombing targets.
Russian Federation was always unhappy that other Islamist groups fighting the Assad regime in Syria have not been excluded by Syria, something Kerry has already hinted might be changed when he referred to these Islamist militants as "subgroups" of ISIS and Nusra.
Assad's fate is a key question in efforts to bring about a negotiated settlement to Syria's five-year civil war.
MOSCOW, July 16 The Kremlin said it was gravely concerned about events in Turkey, and that it had instructed officials to help Russian nationals in Turkey return home at the earliest opportunity.