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, the US president said he was not happy with the whole situation. Trump has previously threatened harsher measures against Russia but did not take action when Putin ignored his deadlines.

Asked if he was prepared to move to the second phase of punishing Moscow, Trump replied: Yeah, I am, though gave no details.

The threat follows remarks from US Treasury Secretary Scott Bessent, who said Washington was prepared to escalate economic pressure but needed Europe stronger backing.

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

So far, Washington's most aggressive measure has been a 50% tariff on imports from India in response to Delhi's continued purchases of Russian oil.

European leaders are expected to travel to Washington early this week to discuss ways of ending the war. Trump said, Certain European leaders are coming over to our country on Monday or Tuesday individually. He also signaled he would speak with Putin in the next couple of days.

In an interview, Ukrainian president Volodymyr Zelensky urged European nations to stop buying Russian energy altogether, stating that all deals must cease if they want to stop Russia's aggression.

Since its invasion of Ukraine in March 2022, Russia has earned around $985 billion from oil and gas.

Despite sanctions, Russia is looking to expand markets and has promised to increase gas supplies to China, while OPEC+ plans to boost production, which might drive down global oil prices.