The US is suspending talks with Russia on a ceasefire agreement for Syria in an apparent final blow to the peace plan forged in September, news reports said on October 3.

The collapse of the talks effectively scuppers hopes of a swift end to Syria's five-year civil war, while inflaming tensions between Moscow and Washington that threaten to damage other areas of cooperation. As the Russian Foreign Ministry said US actions in Syria had allowed militant groups space to reform, President Vladimir Putin ordered the suspension of a crucial plutonium disposal agreement with the US because of Washington’s “unfriendly actions towards Russia”.

The US State Department said Russia was either “unwilling or unable” to get the Syrian government under President Bashar al-Assad to respect the peace deal, while intensified Russian bombing of the besieged city of Aleppo has displaced thousands more people.

Washington’s ambassador to the UN Samantha Power accused Russia of “barbarism” while Russia in turn accused the Pentagon of undermining the ceasefire agreement negotiated last month by US Secretary of State John Kerry and his Russian counterpart Sergei Lavrov. Moscow stressed that it will not halt its air strikes in Syria.

According to the head of the foreign affairs committee in Russia’s upper chamber of parliament, Konstantin Kosachev, the US appeared poised to step up its support of opposition forces in Syria because of “subjective reasons linked to the [US] electoral campaign”.

“The hawks evidently did not support the political process that Lavrov and Kerry agreed on in principle and do not plan on supporting it. And so the process is doomed as things stand,” Kosachev was quoted as saying.

Meanwhile, regarding Russia’s withdrawal from the plutonium agreement, Putin wrote in a decree that the decision reflected “the emergence of a threat to strategic stability and as a result of unfriendly actions by the United States of America against the Russian Federation”.

The agreement signed in 2000 envisages ways of disposing of excessive weapons-grade plutonium in Russia and the US, including the production of mixed oxide fuel to be used in nuclear power reactors, conversion into non-weapons-grade form and also burial. It was expected that both sides will start eliminating declassified amounts of plutonium with a first batch of 34 tonnes of the fuel, enough to make 17,000 nuclear warheads, US diplomats said when the deal was struck.

The Kremlin said it would restore the treaty if the US decreased the size of Nato forces deployed in eastern Europe, ended sanctions against Russia over the Ukrainian conflict, and cancelled the Magnitsky Act, which targets Russian officials implicated in a $230mn tax fraud. The bill also demands that the US compensates Russia for losses incurred as a result of the sanctions.