US President Donald Trump has accused Russian President Vladimir Putin of obstructing attempts to secure a peace deal in Ukraine.

"But it seems that every time I think we're close, he goes and drops ‘another bomb' on somebody, and it's just no good. No good. I'm very surprised," Trump said in an interview with 77 WABC Radio on Tuesday.

The remark came just days after Russia launched its largest aerial barrage since the conflict began, killing four people and setting fire to government buildings in Kiev as a result of intercepted missiles falling back onto the city.

Related News

Kim Jong Un vows DPRK-Russia military alliance to ‘advance nonstop’

Putin responds to US sanctions, says Hungary summit likely postponed

Moscow, however, disputes Trump's claim. Russian officials insist they are not trying to derail negotiations. Instead, Foreign Minister Sergey Lavrov told NBC News in late August that it was Ukrainian President Volodymyr Zelensky who rejected all of Trump's proposals for a settlement during their August 18 meeting in Washington.

Talks have made little headway. Russia has invited Zelensky to Moscow for direct negotiations, even as it launched one of its largest aerial assaults in months, firing hundreds of drones and missiles at Ukrainian cities, including Kharkov and Zaporizhzhia. Meanwhile, Ukraine's allies in Europe are working on a framework of long-term security guarantees, though uncertainty remains over Washington's level of commitment.

At the same time, Trump has warned that if diplomacy continues to stall, Washington is ready to launch a "second stage" of sanctions against Moscow, urging the European Union to join what he described as an impending "economic war." He stressed that while the US would not pursue a military confrontation, he had "something very serious" in mind in terms of economic measures should negotiations fail.

Read more: US envoy urges Europe to send troops for Ukraine security guarantees