BRUSSELS, Belgium, Sept 8, 2025 (BSS/AFP) - The European Union's sanctions envoy David O'Sullivan will lead a delegation for talks with the United States Monday in Washington on stepping up coordination on sanctions on Russia over Ukraine, Brussels said.

An EU official, talking on condition of anonymity, said that O'Sullivan -- who has spearheaded the bloc's global outreach on stopping Moscow's evasion of sanctions -- will hold meetings Monday and Tuesday.

US President Donald Trump threatened Sunday to impose more sanctions on Russia, after the Kremlin unleashed its biggest-ever aerial barrage at Ukraine.

US Treasury Secretary Scott Bessent said Washington was prepared to "increase pressure" on Russia, but that Europe must also act to truly force Moscow to the negotiating table.

"We are talking about what can the two -- EU and the US -- do together. And we are prepared to increase pressure on Russia," Bessent told NBC's "Meet the Press" program.

"But we need our European partners to follow us," he said.

Trump has threatened to penalise countries that buy Russia's oil, seeking to cut off a key funding source for Russian leader Vladimir Putin's war, but has so far only hit India with so-called secondary sanctions.

The EU is currently prepping a new round of sanctions on Russia -- the 19th since the Kremlin's 2022 invasion -- and has said it should include more secondary sanctions on countries helping Moscow circumvent punishment.

In its last package of measures the EU targeted Chinese banks accused of helping facilitate support for Moscow and an oil refinery in India.

But stepping up pressure on India would be politically problematic for the EU as it is looking to improve trade ties with the world's most populous country and fears pushing it closer to Moscow and Beijing.