Moscow has no intention of sending troops into Ukraine, Russian Foreign Minister Sergei Lavrov has said.
His comments came after the US and Russian presidents discussed a possible diplomatic solution to the crisis.
The US-backed plan calls for Russia to halt to its military build-up on the border with Ukraine and withdraw its troops to base in Crimea.
Meanwhile Ukrainian boxer and opposition leader Vitaly Klitschko has pulled out of the race for president.
He announced on Saturday that he was supporting billionaire Petro Poroshenko in elections due in May. Former Prime Minister Yulia Tymoshenko has also said she will stand.
Announcing his withdrawal from the race, Mr Klitschko said: “The only chance of winning is to nominate one candidate from the democratic forces.”
In an interview with state TV channel Rossiya 1 on Saturday, Mr Lavrov said: “We have absolutely no intention of – or interest in – crossing Ukraine’s borders.”
He added that Russia was ready to protect “the rights of Russians and Russian-speaking people in Ukraine, using all available political, diplomatic and legal means”.
After the interview was broadcast, it emerged Mr Lavrov had spoken by phone to US Secretary of State John Kerry, in a conversation that Russian officials said was initiated by the US.
That call followed an hour-long phone discussion late on Friday between Russian President Vladimir Putin and US President Barack Obama. Mr Putin had contacted President Obama, according to US officials.
“President Obama underscored to President Putin that the United States continues to support a diplomatic path… with the aim of de-escalation of the crisis,” the White House said in a statement.
“President Obama made clear that this remains possible only if Russia pulls back its troops and does not take any steps to further violate Ukraine’s territorial integrity and sovereignty.”
The two leaders agreed that Mr Lavrov and Mr Kerry would meet soon to discuss the next steps.
The US proposal, developed in consultation with Ukraine and other European countries, includes halting the military build-up near Ukraine’s border, the deployment of international monitors in Crimea to protect the rights of Russian speakers, and the return of Russian troops there to their bases.
The Kremlin said that the Russian president had drawn Mr Obama’s attention to “the continued rampage of extremists” in Kiev and various regions of Ukraine.
It said these individuals were “committing acts of intimidation towards peaceful residents, government authorities and law enforcement agencies… with impunity”.
Mr Putin suggested examining possible steps the global community could take to help stabilise the situation, the Kremlin statement said.
Russia’s reported troop movements near Ukraine’s eastern border – described by Nato as a “huge military build-up” – has triggered fears that Mr Putin’s interest in Ukraine is not limited to Crimea.
The BBC’s North America Editor, Mark Mardell, said Friday night’s phone call could indicate tentative progress towards a diplomatic solution – just when fears were growing in the West that Russia could be about to stage an invasion of eastern Ukraine.
The US and its allies have imposed sanctions on members of Mr Putin’s inner circle, and threatened to take action to target the Russian economy, in response to Moscow’s actions in Crimea.
Moscow formally annexed Crimea after the predominantly ethnic Russian region held a referendum which backed joining Russia.
Kiev and the West condemned the vote as “illegal”.
The move followed months of street protests, which led to the overthrow of pro-Kremlin Ukrainian President Viktor Yanukovych in February.