The US will withdraw from a landmark nuclear weapons treaty with Russia, President Donald Trump has confirmed.
Speaking to reporters, Trump said Russia had "violated" the 1987 Intermediate-Range Nuclear Forces (INF) treaty.
The deal banned ground-launched medium-range missiles, with a range of between 500 and 5,500km (310-3,400 miles).
The US would not let Russia "go out and do weapons [while] we're not allowed to", Trump said.
"I don't know why President [Barack] Obama didn't negotiate or pull out," the president said after a campaign rally in Nevada. "They've been violating it for many years."
In 2014, President Obama accused Russia of breaching the INF after it allegedly tested a ground-launched cruise missile. He reportedly chose not to withdraw from the treaty under pressure from European leaders, who said such a move could restart an arms race.
A Russian foreign ministry source said the US move was motivated by a "dream of a unipolar world" where it is the only global superpower, state news agency RIA Novosti reported.
The US insists the Russians have, in breach of the deal, developed a new medium-range missile called the the Novator 9M729 - known to Nato as the SSC-8.
It would enable Russia to launch a nuclear strike at Nato countries at very short notice.
Russia has said little about its new missile other than to deny that it is in breach of the agreement.
Analysts say Russia sees such weapons as a cheaper alternative to conventional forces.
The New York Times reported on Friday the US was considering withdrawing from the treaty in a bid to counter China's expanding military presence in the western Pacific.
The country was not a signatory of the deal, allowing it to develop medium-range missiles without restraint.
National Security Adviser John Bolton is expected to tell the Russians of the withdrawal during talks in Moscow later this week.
What is the Intermediate-Range Nuclear Forces (INF) treaty?
Soviet leader Mikhail Gorbachev and US President Ronald Reagan signed the INF treaty in 1987