Cutting out Russian oil supplies ``will hit hard at the main artery of (President Vladimir) Putin's economy and deny him the revenue he needs to fund his war,'' the G-7 countries, which include the U.S., Britain, Canada, Germany, France and Italy and Japan, said in a statement.
``We will ensure that we do so in a timely and orderly fashion, and in ways that provide time for the world to secure alternative supplies,'' they added.
Casting a look back at World War II, the leaders stressed unity in their resolve that Putin must not win.
``We owe it to the memory of all those who fought for freedom in the Second World War, to continue fighting for it today, for the people of Ukraine, Europe and the global community,'' they said.
U.S. President Joe Biden's call with the G7 leaders and Zelenskyy lasted about an hour.
The U.S. also announced new sanctions against Russia for its invasion of Ukraine. They include cutting off Western advertising from Russia's three biggest television stations, banning U.S. accounting and consulting firms from providing services to any Russian, and piling additional restrictions on Russia's industrial sector, including cutting off Moscow from wood products, industrial engines, boilers, bulldozers and more.
The White House announced the new sanctions ahead of the May 9 Victory Day, when Russia traditionally celebrates Nazi Germany's defeat in 1945 with huge military parades.
Putin is expected to talk about what it calls its special military operation in Ukraine and address troops on Red Square on Monday.
The U.S. and European allies were seeking to offer counter-messaging that Putin is further isolating Russia from the rest of the world and doing enormous harm to the Russian economy.
Ahead of the call, U.K. officials said Britain will provide an extra 1.3 billion pounds ($1.6 billion) in military support to Ukraine to help the nation defend itself against Russian forces.
The funding, which comes from British government reserves, includes 300 million pounds of military kit promised by Prime Minister Boris Johnson earlier this week, such as radar systems to target Russian artillery, GPS jamming equipment and night vision devices.
Canadian Prime Minister Justin Trudeau made a surprise visit to Ukraine Sunday, touring the northern town of Irpin, which had been heavily damaged by Russia's attempt to take the capital of Kyiv at the start of the war. The mayor on Sunday posted images of Trudeau on social media, saying that the Canadian leader was shocked by the damage he saw at civilian homes.
Trudeau's office later said ``the prime minister is in Ukraine to meet with President Zelenskyy and reaffirm Canada's unwavering support for the Ukrainian people.''
Jill Biden also made an unannounced visit on Sunday, holding a surprise Mother's Day meeting in western Ukraine with first lady Olena Zelenska. Biden traveled under the cloak of secrecy, becoming the latest high-profile American to enter Ukraine during its 10-week-old war with Russia.
``I wanted to come on Mother's Day,'' the U.S. first lady told Zelenska. ``I thought it was important to show the Ukrainian people that this war has to stop and this war has been brutal and that the people of the United States stand with the people of Ukraine.''
In Germany, Chancellor Olaf Scholz said in a televised address that Sunday was ``a May 8th like no other.''
He said Germany has worked hard to own up to its actions during World War II, reconciling with both Russia and Ukraine and committing itself to the concept of ``never again.'' But Russia's ``barbaric'' invasion of Ukraine in February has brought war back to Europe, Scholz said, a prospect that once seemed unthinkable.
``Freedom and security will prevail -- just as freedom and security triumphed over lack of freedom, violence and dictatorship 77 years ago,`` Scholz said in his address.
German Bundestag President Barbel Bas, the second highest-ranking German official after the president, met Sunday with Zelenskyy in Kyiv and attended a memorial event honoring the anniversary of the end of World War II.
``We really appreciate that on the Day of Remembrance and Reconciliation itself, and in what for us is such a trying time of war, the President of the German Bundestag Barbel Bas came to support Ukraine,'' said a post published Sunday on Zelenskyy's Telegram channel.
Ukrainian Prime Minister Denys Shmyhal posted a photo of himself shaking hands with Bas on Twitter. He wrote that Ukraine is counting on Germany's support to recover Ukraine and join the European Union's 27 nations.
Croatia's prime minister was also in Ukraine on Sunday following reports that a Croatian citizen fighting in Mariupol was captured by Russian forces. The Croatian government said the visit by Prime Minister Andrej Plenkovic presented ``an expression of solidarity and support'' with the Ukrainian leadership and the people.