Moscow reserved the right to use its armed forces to protect Russians in Ukraine, Russian President Vladimir Putin said, and accused the West of encouraging an "unconstitutional coup" there.
In his first comments on Ukraine since its fugitive president fled to Russia, Putin yesterday denied he had already deployed troops there and said he saw no immediate need to invade eastern Ukraine.
Watch: Obama: Russia in "violation of international law" in Ukraine
Putin also held a telephone conversation with President Xi Jinping on the situation. While the Kremlin statement described their positions on the issue as "close", the Chinese foreign ministry said that Xi had urged Putin to engage all parties to resolve the crisis, noting the situation affected both regional and global politics.
Tensions remained high in Crimea, with troops loyal to Moscow firing warning shots to ward off protesting Ukrainian soldiers.
In Washington, US President Barack Obama said Putin's rationale for Russia's incursion into Crimea was not "fooling anybody", and said its "meddling" would push states away from Moscow.
US Secretary of State John Kerry, who arrived in Kiev to meet Ukraine's interim government, said Moscow would face more pressure if it failed to de-escalate tensions. The US government also announced an aid package of US$1 billion in energy subsidies for Ukraine.
A rift appeared to be opening between the US and Europe on how to punish Russia, with European capitals resisting Washington's push towards sanctions. The American position is supported by parts of eastern Europe and Sweden. But in Brussels, the foreign ministers of Germany, France, Italy and Spain resisted calls for trade sanctions.
Putin said ousted president Viktor Yanukovych remained Ukraine's only legitimate leader despite fleeing to Russia, but conceded he lacked any political future. "I think he has no political future, I told him that. As for playing a role in his fate, we did that purely for humanitarian reasons," Putin said.
Stock markets around the world seemed to recover from their fright over the Ukrainian situation, clawing back a chunk of Monday's losses.
Additional reporting by The Guardian, Agence France-Presse