US President Joe Biden was meeting with G7 allies Thursday to hammer out a raft of new sanctions against Russia after it invaded Ukraine, and will later speak to the American people on a crisis that he warns will cause "catastrophic loss of life."

The virtual, closed-door meeting of G7 leaders -- Britain, Canada, France, Germany, Italy, Japan and the United States -- was set to start at 9:00 am (1400 GMT), with Biden's White House speech scheduled for early afternoon.

For weeks, as Russia built up tens of thousands of troops and heavy weapons on Ukraine's border, Biden has led NATO and other European allies in trying to craft a package of what Washington says are "unprecedented" sanctions as a deterrent.

Now that the deterrent has failed, the effort is likely to see rapid escalation to inflict real pain on Russia's already shaky economy.

"The United States and its allies and partners will respond in a united and decisive way. The world will hold Russia accountable," Biden said in his first comments late Wednesday in Washington, after Russian missiles began to rain down on Ukraine.

Biden also held a phone call with his Ukrainian counterpart Volodymyr Zelensky, saying afterwards that he had promised to "provide support and assistance to Ukraine and the Ukrainian people."

The US president noted that Zelensky had requested him to "call on the leaders of the world to speak out clearly" against Putin's "flagrant aggression."

On Tuesday, after Putin first announced he would send troops as "peacekeepers" to two small areas already controlled by Moscow-backed separatists, Western countries swung into action.

The US government joined European allies in imposing sanctions on two Russian banks, Moscow's sovereign debt, several oligarchs and other measures.
And on Wednesday, as the Russian invasion force became clearly primed to attack, Biden announced he was imposing sanctions on the Nord Stream 2 natural gas pipeline from Russia to Germany -- one of energy-rich Moscow's highest-profile geopolitical projects.

Germany had earlier announced it would block the pipeline from opening for deliveries.

US officials say tougher new sanctions will include targeting other, bigger banks, more oligarchs close to Putin and, crucially, a ban on exports to Russia of high-tech equipment and components. It was not clear how many of these measures would be announced Thursday.

Some measures also risk serious economic fallout for Western countries and could imperil the global economy recovery after the Covid pandemic. Already stock markets are tumbling and oil prices are soaring over $100 a barrel.

- 'Death and destruction' -

Soon after the Russian attacks began, US senators from both parties indicated support for a tough response.

"Tonight, the entire post-World War international order sits on a knife edge. If Putin does not pay a devastating price for this transgression, then our own security will soon be at risk," Democratic Senator Chris Murphy said.

Another Democrat, Senator Mark Warner, said "President Biden has already imposed an initial tranche of sanctions, and it is now time for us to up the pain level for the Russian government."

Russians "will pay a steep cost for Putin's reckless ambition, in blood and in economic harm," he said.

Republican Senator Mitt Romney warned against "the peril of again looking away from Putin's tyranny" and urging "the harshest economic penalties" and "expelling them from global institutions."

In his statement, Biden said "the prayers of the entire world are with the people of Ukraine tonight as they suffer an unprovoked and unjustified attack by Russian military forces. President Putin has chosen a premeditated war that will bring a catastrophic loss of life and human suffering." - AFP