UK Foreign Secretary Liz Truss is to seek agreement from the international community to step up support for Ukraine, in the face of continuing attacks from Russian forces.
Foreign ministers from across the West are gathering in Brussels to consider how to maintain pressure on Russia.
Ahead of the trip, Ms Truss said allies were prepared to “tighten the vice around Putin’s war machine”.
Europe’s dependency on Russian oil and gas is also likely to be discussed.
Meanwhile, Home Secretary Priti Patel is visiting Poland to launch a new family scheme for Ukrainian refugees.
Under the extended scheme, which was announced earlier this week, British nationals and anyone settled in the UK will be able to apply to bring their parents, grandparents and siblings to the country.
The UK’s initial visa offer was restricted to immediate family, including children and partners.
In Brussels, the foreign secretary will call on her counterparts from Nato, the G7 and EU to “embrace reliable partners rather than be dependant and beholden on any one country” for oil or gas.
Ms Truss, who called it “one of the biggest days of diplomacy”, said co-operation between the UK and EU was “essential to defend European security”.
“We will work with fellow freedom-loving democracies to tighten the vice around Putin’s war machine and signal our strong support for Ukraine’s territorial integrity,” she added.
Russian President Vladimir Putin has insisted the war in Ukraine is “going to plan”, despite taking only one major city – Kherson in the south.
Elsewhere, Ukrainian President Volodymyr Zelensky has accused Russia of “nuclear terror” after it bombarded a large nuclear power station, causing a fire.
The authorities say the Zaporizhzhya plant – which is the biggest of its kind in Europe – is secure and radiation levels are normal.
It comes after President Zelensky asked Mr Putin for one-to-one talks, saying it was the only way to end the war. He has also appealed to Nato to supply warplanes.
Russia attacks Ukraine: More coverage
While defensive weapons have been sent to Ukraine, the West has largely responded to the invasion with economic sanctions against Russian individuals, businesses and banks.
On Thursday the UK announced sanctions on two more Russian oligarchs – Alisher Usmanov, a billionaire whose company previously had links with Arsenal football club – and Igor Shuvalov, a former deputy prime minister to Mr Putin.
Their assets will be frozen and they will be banned from travelling to the UK. British citizens and businesses will not be allowed to deal with them.
But there have been calls for swifter and more thorough clampdowns on oligarchs, with the UK accused of being slower than its European neighbours and facing legal hold-ups preventing sanctions – claims rejected by Downing Street.
There are fears that oligarchs will sell property and move money and assets out of the UK before they are targeted. Ministers have set up a taskforce to look into individual cases.
Deputy Prime Minister Dominic Raab said he would support seizing property in the UK owned by wealthy Russians with links to Mr Putin, as long as the government has “the evidence and there is the legal basis” to do so.
Mr Raab also confirmed to LBC he would support housing Ukrainian refugees in any seized properties, a move called for by the Liberal Democrats.
He also said the government is looking at ways to stop lawsuits being used by wealthy individuals to intimidate journalists and organisations looking into sources of their wealth. Mr Raab is expected to explore options including regulatory reform and potential legislation.
Mr Raab said wealthy people connected to the Russian president were abusing libel laws to intimidate individuals and organisations highlighting corruption in Russia.
He told BBC Breakfast: “It cannot be right that kleptocrats and those with links to Putin can silence those shining a light on those excesses, and use our courts to do so.”
Meanwhile on Friday, the home secretary will meet Ukrainians applying for the UK’s family scheme in Medyka, near the border with Ukraine.
Ms Patel said the extended scheme would enable Ukrainians with family in the UK “to be welcomed safely, quickly and free of charge”.
Under the scheme, normal requirements for salary or language tests will be waived and checks will be accelerated to process applications as quickly as possible, the Home Office said.
It added that “essential security checks” would still take place “given the malign action being taken by the Russian state to infiltrate Ukraine”.
It said the family scheme would be followed up by another for Ukrainians with no ties to the UK – with further details to be set out “in due course”
However, Labour called for the creation of a simple emergency visa, valid for 12 months, allowing anyone fleeing the conflict to come to the UK, with normal visa conditions other than biometrics and security checks lifted.
More than one million Ukrainians have fled the country since the invasion began last week, according to the United Nations, with most heading for neighbouring countries.
So far, the UK has sent three planes with 320,000 medical items to help – and the UK’s Disasters Emergency Committee has launched an appeal.