SINGAPORE, May 30, 2025 (BSS/AFP) - French President Emmanuel Macron said on Friday that Washington faces a "credibility test" over its response to Russia dragging its feet on a Ukraine ceasefire.

Moscow has rebuffed calls for an immediate ceasefire and kept up an intense bombardment of Ukraine even as diplomatic efforts to end the war have gained momentum.

US President Donald Trump called Vladimir Putin "crazy" late on Sunday in a rare rebuke of the Russian leader but he has yet to follow up on repeated threats to impose fresh sanctions on Moscow.

Macron said that if Russia gives "confirmation that it is not ready to make peace" Washington must then confirm its "commitment" to impose sanctions on Moscow, stressing it was a "credibility test for the Americans".

"I spoke 48 hours ago to President Trump who showed his impatience. The question now is what do we do? We (Europeans) are ready," he said during a visit to Singapore.

Macron will give the opening speech at the Shangri-La Dialogue in Singapore, Asia's main annual security and defence conference, which was addressed last year by Ukrainian President Volodymyr Zelensky.

The French leader said this week he believed Trump now realised Putin lied when he claimed to be ready for peace in Ukraine, and hoped the US president's anger would translate into action.

Macron said it was time to threaten Russia with "much more massive sanctions" to persuade it to end the conflict begun by its invasion of Ukraine in 2022.

The French president visited Kyiv on May 10 with other European leaders to give Russia an ultimatum -- agreed with Washington -- to accept a ceasefire.

The Russian offensive has resulted in tens of thousands of deaths and the destruction of large parts of eastern and southern Ukraine.