Russian President Vladimir Putin signed a law on Monday terminating an already defunct plutonium disposal agreement with the United States that aimed to prevent both sides from building more nuclear weapons.

The move comes as ties cool between Putin and US President Donald Trump, who has expressed mounting frustration at his Russian counterpart for refusing to accept a peace deal in Ukraine.

Trump scrapped plans for a peace summit with Putin last week, saying it would have been a "waste of time", and ruled out rescheduling unless the Russian leader sent signals he would agree to a deal.

The Plutonium Management and Disposition Agreement, signed in 2000 and amended in 2010, committed Moscow and Washington to reduce their vast Cold War-era stockpiles of plutonium by 34 metric tonnes each

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