Oil prices hit their highest level since 2008 after the US said it was discussing a potential ban on Russian supplies with other countries.
Brent crude - the global oil benchmark - rose to above $139 a barrel overnight, before easing to around $130 this morning.
On Sunday, the US Secretary of State Antony Blinken said the Biden administration and its allies were discussing a ban on Russian oil supplies.
"We are now in very active discussions with our European partners about banning the import of Russian oil to our country while, of course, at the same time, maintaining a steady global supply of oil," the US's chief diplomat said.
He pointed out that the sanctions western governments have imposed so far have already had a "major impact" on Russia's economy.
He added: "The actions we've taken to date have already had a devastating impact on the Russian economy. We see the ruble in free-fall, we see the economy heading into a deep recession.
"We've already had a major impact. But we are looking, again, as we speak, in coordination with our allies and partners at this process of banning oil imports."
Escalation
Later, US House of Representatives Speaker Nancy Pelosi said the chamber was "exploring" legislation to ban the import of Russian oil and that Congress this week intended to enact $10bn (£7.6bn) of aid for Ukraine in response to Russia's military invasion.
"The House is currently exploring strong legislation that will further isolate Russia from the global economy," Ms Pelosi said in a letter.
A Russian oil embargo would be a major escalation in the response to the invasion of Ukraine and would potentially have a major impact on the global economy.
Sturgeon pressure
Meanwhile, Nicola Sturgeon is under pressure from senior colleagues to end her hostility to North Sea oil and gas exploration in the face of the Ukraine crisis, with Westminster leader Ian Blackford warning that buying Russian energy funds Vladimir Putin’s war machine.
The first minister has taken an increasingly hard line on fossil fuels since the Cop26 climate summit in Glasgow last October, calling for an end to oil and gas exploration in order to reduce environmentally damaging emissions.
Former SNP energy minister Fergus Ewing argues that voluntarily ceasing exploration in the North Sea would actually increase Scotland’s carbon footprint by making it more reliant on fossil fuels from other countries.
Writing in The Sunday Times at the weekend, Ewing and Alistair Carmichael, the Liberal Democrat MP for Orkney and Shetland, say the grim events in Ukraine “should give us all cause to be open-eyed about our approach to energy policy”.