Following last week's sharp escalation in diplomacy between the US and Russia, when John Kerry warned of not only breaking off diplomatic relations over Syria with Russia, and threatening to use "military force" including potentially US-based ground forces in Syria for the first time, but also slamming Russian strikes over Aleppo as "barbaric", Russia responded Monday when Russian President Vladimir Putin suspended an agreement with the United States for disposal of weapons-grade plutonium because of "unfriendly" acts by Washington, the Kremlin said.

A Kremlin spokesman cited by Reuters said Putin had signed a decree suspending the 2010 agreement under which each side committed to destroy tonnes of weapons-grade material because Washington had not been implementing it and because of current tensions in relations. The deal, signed in 2000 but which did not come into force until 2010, was being suspended due to "the emergence of a threat to strategic stability and as a result of unfriendly actions by the United States of America towards the Russian Federation", the preamble to the decree said.

It also said that Washington had failed "to ensure the implementation of its obligations to utilize surplus weapons-grade plutonium". The 2010 agreement, signed by Russian Foreign Minister Sergei Lavrov and then-U.S. Secretary of State Hillary Clinton, called on each side to dispose of 34 tonnes of plutonium by burning in nuclear reactors.

Clinton said at the time that that was enough material to make almost 17,000 nuclear weapons. Both sides then viewed the deal as a sign of increased cooperation between the two former adversaries toward a joint goal of nuclear non-proliferation.

"For quite a long time, Russia had been implementing it (the agreement) unilaterally," Kremlin spokesman Dmitry Peskov told a conference call with journalists on Monday. "Now, taking into account this tension (in relations) in general ... the Russian side considers it impossible for the current state of things to last any longer."

Furthermore, later in the day, Russia's deputy foreign minister said that information between Russian and US military has stopped of late despite Moscow’s commitment, Russia’s Deputy Foreign Minister Gennady Gatilov said on Monday. "All contacts between the military have been stopped of late, there has been no exchange of information," he said as Russian Tass news agency reported.

Gatilov however noted that Russia was trying to agree with the US on resumption of truce in Syria.

"We are trying to agree with Americans on resumption of truce in Syria," Gatilov said but he said it has not been done yet despite regular contacts between the Russian and US top diplomats.

"Although what has been written in the September 9 document gives a good opportunity to get the process of Syrian settlement moving," Gatilov said. He stressed that the Russian side was not discussing with the US the future of Syrian President Bashar al-Assad.

"We are not discussing this issue - the fate of Assad, with them," the diplomat said.

The diplomat also noted that Moscow is not going to to back France’s politicized resolution on Aleppo in the UN Security Council. Moscow plans to submit amendments to France’s draft resolution on Syria.

"This draft invites a lot of questions from us. Literally on Friday or Saturday, France once again pushed its draft resolution on humanitarian situation in Aleppo," he said.

"We are fundamentally against such politicized moves, aimed at using the UN Security Council for putting additional pressure on Syria and Russia. We regard this move by France as one more among these actions," Gatilov said.

According to the deputy minister, establishment of any new Syria monitoring mechanism is currently out of the question.

"[France’s draft resolution on Aleppo] has a proposal to create a certain monitoring of fulfillment of humanitarian commitments," Gatilov said in response to a question from TASS. "But creating some monitoring again with an unclear mandate and goals - why should it be done? Geneva has a task force on humanitarian issues, which discusses these issues, the situation with humanitarian access etc.," he said.

There was some good news: in a sign that relations are not irrevocably broken, the official pointed out that Russia was prepared for restoring two-day humanitarian pauses near Aleppo for letting through humanitarian convoys. "Our military are ready for introducing 48-hour-long humanitarian pauses near Aleppo," he said.

"As for humanitarian pauses, we’ve said in New York and in Geneva again and again that we are ready for restoring 48-hour pauses for arranging humanitarian convoys for eastern Aleppo," Gatilov said. "Regrettably, the Americans do not support the call, and this is a stumbling block in our contacts."

It remains unclear if the US is eager to re-engage the peace process with Russia in Syria, especially after last month's unexpected attack by US-coalition forces on Syrian troops, and the dramatic pick up in anti-Russian rhetoric in the western media over the past two weeks.