President Trump prevented some new sanctions on Russia and hefty tariffs on large-scale buyers of Russian oil from taking effect late Friday, waiving portions of a bipartisan law aimed at pressuring the Russian government — as Mr. Trump seeks to ease prices by tapping Russian energy.

Tariffs of 100% on the world's five largest importers of Russian crude oil and natural gas were set to take effect on Sunday under the Lindsey O. Graham Sanctioning Russia Act, which Mr. Trump signed late last month. But the law gives the president the authority to waive portions of the law if he certifies to Congress that halting the sanctions is "in the national interests of the United States," a provision that Mr. Trump invoked in an executive order Friday.

The president said he sent a notification to Congress.

He also waived the law's 500% tariffs on Russian goods, and halted certain other sanctions on Russia. He said the waivers will remain in place until administration officials "determine that further action is appropriate," and directed members of his administration to "monitor" countries that import Russian energy or evade sanctions.

An envoy to Russian President Vladimir Putin praised Mr. Trump's decision on Saturday.

"The Trump administration's suspension of the Graham Act is an important and truly historic moment," Kirill Dmitriev said in a post on social media.

In a social media post highlighting the aftermath of an attack on Ukraine's energy sector, Ukrainian President Volodymyr Zelenskyy said the decision was "unfortunate," adding that the Graham Act "could have helped enormously."

"A U.S. sanctions blackout, easing pressure on the aggressor, financial rewards for Putin - all of this only encourages him to keep attacking," Zelensky said in the post.

The law — championed by the late Sen. Lindsey Graham, who died before it was passed — largely took aim at the world's largest buyers of Russian oil and gas, including China, India and Turkey. The European Union has also historically purchased large quantities of natural gas from Russia, but it has cut imports significantly in recent years.

The Friday night waivers came one week after Mr. Trump eased sanctions on Russian diesel and announced a deal with Russian President Vladimir Putin to import diesel to the U.S. market.

The moves mark an about-face for the United States, which has imposed tight restrictions on Russian oil and gas for years — and urged other countries to follow suit — in an effort to prevent Putin from using his country's energy wealth to finance his invasion of Ukraine.

But as oil prices remain high after spiking due to the Iran war, Mr. Trump has increasingly turned his attention to Russia and Ukraine, arguing that war in Ukraine has pushed up energy prices.

Mr. Trump pressed both countries to stop attacking each other's energy infrastructure last weekend, announcing an "energy ceasefire." Ukrainian President Volodymyr Zelenskyy initially said he was willing to abide by an energy ceasefire, but after Russian attacks continued, he said earlier this week that Ukraine would no longer hold off on striking Russian refineries.

The U.S. president has lashed out at Zelenskyy, saying he is "not a big fan."

The decision to ease sanctions has drawn pushback in Congress. Earlier this week, a bipartisan group of senators called the diesel waivers a "betrayal of the people of Ukraine," and urged Mr. Trump to enforce the sanctions and tariffs laid out in the Graham law.

"These authorities require you to apply economic pressure on Russia and the chief enablers of its war, in particular China, and thereby enhance your negotiating position to bring a swift end to this ruinous conflict," they wrote.

In:

• Donald Trump
• Russia
• Trump Administration
• Vladimir Putin
• Volodymyr Zelenskyy
• Lindsey Graham