US President Donald Trump has used his executive authority to block a series of sanctions on Russia that were recently passed by Congress, in a move that has drawn sharp condemnation from Ukraine, European allies, and members of his own party.

In an executive order issued on Friday, Trump said it was in the United States' "national interests" to withhold the sanctions. He had signed the underlying legislation into law in September, and it was due to take effect on Sunday, 18 October.

The law is named after the late Republican Senator Lindsey Graham of South Carolina, who was one of Ukraine's most prominent defenders in Washington before his death on 11 July. The legislation targeted Russia's economy and granted Trump broad powers to impose tariffs of up to 100 percent on the top five purchasers of Russian oil and gas, most significantly China and India.

The law also included sanctions against Russian President Vladimir Putin, senior Russian government officials, banks and other financial institutions, and Russia's so-called "shadow fleet" of tankers used to circumvent existing restrictions.

On Thursday, a bipartisan group of 20 lawmakers sent a letter urging Trump to respect the new law. They thanked him for signing the bill and called for its "full and faithful implementation," saying it would be "decisive in forcing Putin to take peace talks seriously." They urged the administration "to apply the Graham law's sanctions to their fullest extent and without delay."

Trump's decision to waive the sanctions follows his announcement on 9 October that he had held a phone call with Putin and agreed to purchase diesel from Russia. Since a war with Iran began in February, US fuel prices, particularly diesel, have risen sharply, adding to financial pressure on American voters ahead of midterm elections in November, which will determine which party controls Congress.

US allies criticised the diesel deal, expressing concern that it could benefit Russia's war effort. Ukrainian President Volodymyr Zelenskyy called the arrangement a gift to Putin amounting to "an investment in a war that must be ended."

Democrats have been among the most vocal critics of Trump's latest move. Virginia Congressman Don Beyer accused the president of capitulating to Moscow and abandoning Kyiv. "Trump's latest surrender to Putin again betrays our Ukrainian partners and defies clear congressional intent of legislation designed to punish Russia for its illegal war of aggression," Beyer wrote on social media.

The sanctions waiver comes amid a broader deterioration in relations between Washington and Kyiv. On 11 October, Trump claimed that Russia and Ukraine had agreed to an "energy ceasefire," describing it as "effective immediately" but offering no details. Zelenskyy expressed surprise at the announcement but said Ukraine would halt strikes if Russia did the same. Moscow denied ever agreeing to the deal and continued its attacks. After three days, Kyiv resumed its strikes.

Trump responded with sharp criticism, calling Ukraine's strikes on Russian oil refineries a "disgrace." Zelenskyy replied that he was "only standing up for Ukraine's interests."

Tensions were further inflamed earlier in the week when restrictions were placed on the US-owned Starlink satellite internet network, which is critical to Ukraine's military communications. During a slowdown on Tuesday night, Russia launched several deadly strikes on Ukraine, with residents and the government saying there had been no prior warning.

On Friday, Zelenskyy described the disruption as a "very dangerous and unpleasant surprise," adding that Starlink speeds had still not been fully restored.

The Trump administration had previously warned it could withhold intelligence-sharing, which is crucial to Ukraine's defences, if Kyiv did not stop striking Russian oil infrastructure.

In a related development, troops from Britain, France, and Germany are set to take part in a major military exercise in Poland next month. UK Defence Secretary Wes Streeting said the drill was "to ensure we are ready to support the military training and post-war rebuilding that Ukraine will need."