Ukrainian President Volodymyr Zelensky has said he “cannot tolerate any indecisiveness” ahead of the West imposing further sanctions on Russia.
The US said on Tuesday the measures will target financial and state-owned bodies, some officials and oligarchs.
Media reports suggest Russian President Vladimir Putin’s daughters will be among those on the list.
The European Union is also expected to cut off Russian coal imports as concern over alleged war crimes increases.
But Mr Zelensky, speaking to the Irish parliament on Wednesday, said there was still a need to convince some in Europe who believe “war and war crimes are not as horrific as financial losses” to back tougher sanctions.
He added that “Russian oil cannot feed the Russian military machine”, with Ukraine’s foreign minister arguing on Twitter that an embargo on gas and oil was needed to truly impact Russia’s ability to finance the war.
Josep Borrell, the EU’s chief diplomat, separately acknowledged on Wednesday that the one billion euros ($1.09bn; £833m) Europe spent on Russian energy every day put into sharp perspective the billion euros given to Ukraine in military assistance since the start of the invasion.
Some European member states, including Germany, are heavily reliant on Russian energy and had been reluctant to directly target the sector.
However, in a first, the European Commission proposed a potential ban on imports of Russian coal on Tuesday, which must be agreed by all 27 members. Europe buys around €4bn ($4.4bn; £3.3bn) worth of coal from Moscow every year.
Sentiment appeared to change after evidence of Russian war crimes emerged, with French President Emmanuel Macron joining calls for a ban on coal earlier this week.
The ban was suggested ahead of a range of sanctions set to be announced in coordination with the US and other G7 nations.
White House spokesperson Jen Psaki said on Tuesday a number were aimed at “holding accountable the Russian kleptocracy that funds and supports Putin’s war”.
Ms Psaki told reporters that the sanctions, which are expected to include a ban on all new investment in Russia, will “degrade key instruments of Russian state power, impose acute and immediate economic harm on Russia”.
The Wall Street Journal said on Tuesday that Sberbank, Russia’s largest lender, may be among those targeted.
Ms Psaki refused to comment on the reports that Mr Putin’s daughters would be targeted.
European member states are also expected to impose a “full transaction ban” on four Russian banks and ban a range of other Russian and Belarusian imports, including wood, cement, seafood and liquor, worth €5.5 billion ($6bn; £4.59bn).
And Ursula von der Leyen, the European Commission president, said she intends to close EU ports to Russian vessels and ban Russian and Belarusian road transport operators from the region.
Ms Von der Leyen accused Russia of “waging a cruel and ruthless war” against Ukrainian civilians and said the EU must “sustain utmost pressure on Putin and the Russian government at this critical point”.
But Lithuanian Foreign Minister Gabrielius Landsbergis on Tuesday evening criticized the EU’s proposed sanctions package, calling it a “feeble response” which is “an invitation for more atrocities.”
“Coal, four banks…a ban on ports and borders (with exceptions) is not really an adequate sanctions package to the massacres that are being uncovered,” Mr Landsbergis wrote on Twitter.