US President Joe Biden on Tuesday announced the "first tranche" of sanctions against Russia, including steps to starve the country of financing, saying Moscow had started an invasion of Ukraine.

And Biden threatened tougher steps if Russia "continues its aggression."

"We're implementing sanctions on Russia's sovereign debt. That means we've cut off Russia's government from Western financing," Biden said.

"It can no longer raise money from the West and cannot trade in its new debt on our markets or European markets either."

The measures also target VEB, Russia's state development bank, and members of the country's "elites," the US leader said.

"They share the corrupt gains of the Kremlin policies, and should share in the pain as well."

The announcement came after the European Union unveiled its own sanctions in a coordinated Western effort to pressure Russian leader Vladimir Putin.

Biden said the responses "have been closely coordinated with our allies and partners" and added, "We'll continue to escalate sanctions if Russia escalates."

However, Washington's response did not seem to go as far as the European Union, nor as far as some expected.

Biden announced "full blocking sanctions" on both VEB and Russia's "military bank," which likely means the institutions will have their foreign assets frozen and will be prohibited from using the US financial system.

However, the penalties cover fewer financial institutions, and do not appear to have severed the country from the SWIFT system used to move money around the globe.

Nor did Biden resort to export controls, which would have cut Russian firms off from key high-tech equipment and software, which some analysts said was a possibility.