Donald Trump has threatened tougher sanctions against Russia after its heaviest aerial bombardment on Ukraine since the war began.

Sunday's strikes killed four people, including a mother and her baby, and damaged Ukraine's main government building in Kyiv for the first time. The attack - which Ukraine said involved at least 810 drones and 13 missiles - has led to growing calls for stronger Western action against President Vladimir Putin.

Kremlin's spokesman Dmitry Peskov said Monday that no sanctions would ever be able to force Russia to change the consistent position that our president has repeatedly spoken about.

Speaking to reporters after the bombardment, Trump said he was not happy with the whole situation. Trump has previously threatened harsher measures against Russia but did not take any action when Putin ignored his deadlines and threats of sanctions.

When asked if he was prepared to move to the second phase of punishing Moscow, Trump responded: Yeah, I am, though he did not provide any specific details.

The threat follows remarks from US Treasury Secretary Scott Bessent, who indicated that Washington was ready to escalate economic pressure but required stronger backing from European allies.

In an interview with NBC, Bessent stated that, if EU nations increased sanctions and imposed secondary tariffs on countries purchasing Russian oil, the Russian economy will be in total collapse, and that will bring President Putin to the table.

Bessent warned of a race between how long the Ukrainian military could hold out and how long the Russian economy could withstand sanctions.

Washington's most aggressive measure so far has been a 50% tariff on imports from India, enacted last month in response to Delhi's continued purchases of Russian oil. Trump has floated the idea of extending such secondary sanctions to other countries but has yet to proactively follow through.

European leaders are expected to visit Washington early this week to discuss strategies for ending the war, as Trump indicated. He mentioned that certain European leaders are coming over to our country on Monday or Tuesday individually, without specifying who they were.

Ukrainian President Volodymyr Zelensky has urged European nations to completely cease energy purchases from Russia. He asserted, We have to stop [buying] any kind of energy from Russia, and by the way, anything, any deals with Russia. We can't have any deals if we want to stop them. Zelensky praised Trump's tariff strategy as the right idea to sever Moscow's revenue sources.

Since its full-scale invasion of Ukraine in March 2022, Russia has reportedly earned around $985 billion (£729 billion) from oil and gas sales, with China and India being the largest buyers, while the EU has reduced, but not entirely halted, its purchases.

Despite sanctions, Russia aims to expand its markets. During a recent meeting in Beijing, Moscow announced plans to increase its gas supplies to China. Meanwhile, OPEC+, which includes Russia, has agreed to boost oil production, a move that could lower global oil prices and complicate Western efforts to constrict Moscow's finances.