US President Barack Obama on Wednesday called on Russia to agree strategic nuclear weapons cuts of up to a third and to also rein in strategic atomic arms, but got the cold shoulder from Moscow.
In a major speech in Berlin, Obama also committed to attend a Nuclear Security summit, designed to deprive terror groups of nuclear materials, in The Hague next year and to hold his own in his last year as president in 2016.
"These are steps we can take to create a world of peace with justice," Obama said, speaking with Berlin's iconic Brandenburg Gate as a backdrop.
Under the new Strategic Arms Reduction Treaty (START) negotiated with Moscow during Obama's first term, the two former Cold War foes cut strategic nuclear weapons stocks to the 1,550 level.
A one-third cut in the arsenals would take them to the 1,000 weapons mark.
Russia has previously resisted cuts to the number of tactical nuclear weapons stationed in Europe, and President Vladimir Putin said ahead of Obama's speech that Russia would not allow an imbalance in nuclear forces.
"We cannot allow the balance of the system of strategic deterrence to be disturbed or the effectiveness of our nuclear force to be decreased," Putin was quoted by Russian news agencies as saying.
After the speech, Russian deputy prime minister Dmitry Rogozin suggested that Obama's plan was a non-starter while Washington was developing its missile defence systems.
"How can we take seriously this idea about cuts in strategic nuclear potential while the United States is developing its" capabilities to intercept Russia's weapons, Rogozin asked.
"Clearly, (Russia's) political leadership cannot take these assurances seriously," said Rogozin, who oversees the defence sector and the nuclear industry, according to the state-owned Itar-TASS news agency.
"The offence arms race leads to a defence arms race and vice versa," he said, speaking after a government meeting in Saint Petersburg that focused on Russia's defence sector.
Obama has made cutting nuclear weapons stocks a centrepiece of his political legacy and is in theory committed to eradicating them altogether.
His move Wednesday places the idea of arms cuts in play in the runup to his next summit with Putin in Moscow in September. The two leaders, estranged on Syria policy, held a frosty meeting in Northern Ireland on Monday.
The proposals were welcomed by the community of nuclear arms scientists and experts in Washington.
"It is difficult to imagine a military mission that requires even one nuclear weapon -- the use of 10 is unthinkable; yet we have over 7,000 in our arsenal," said Joe Cirincione, president of the Ploughshares Fund.
"President Obama detailed a smart security strategy to reduce US and Russian nuclear weapons, secure all global stocks of weapons material and prevent new nuclear nations."
Philip Coyle, senior science fellow at the Center for Arms Control and Proliferation, said a Cold War ideology had permeated Washington for too long.
"The president spoke about several key policies that will make America safer in the short and long term," he said.
But there were signs that Obama, even if Russia should agree to a treaty on arms reductions, would struggle to get it ratified by the US Senate -- especially when lame duck status begins to set in later in his presidency.
The top Republican on the Senate Foreign Relations Committee, Bob Corker, said that reducing US nuclear stocks without modernising the US arsenal to replace ageing current warheads would amount to "unilateral" disarmament.
Such comments have prompted some experts to suggest that Obama could try to negotiate nuclear weapons stocks with Russia without trying to conclude a formal treaty.
But Corker said that he had been told by Secretary of State John Kerry that any reductions would occur in bilateral treaty negotiations and would be subject to Senate approval.
Obama was forced to pull out all the stops to get his earlier START treaty with Russia ratified.
The president inaugurated the first Nuclear Security summit in Washington in 2010 and went to a follow-up meeting in Seoul two years later.