Oil fluctuated as the market weighed Donald Trump's mixed remarks about the threat of fresh penalties on Russian crude if his counterpart Vladimir Putin refuses a ceasefire with Ukraine.

Trump told reporters on Air Force One that he doesn't think Putin will "go back on his word," which appeared to take some of the edge off his criticism earlier Sunday, when NBC News reported him as saying he was "very angry" at the Russian president and would consider "secondary tariffs."

Brent's June contract was little changed below $73 a barrel after a marginal gain at the open, while West Texas Intermediate was near $69. Trump's threat comes ahead of so-called reciprocal US levies this week on other nations that could lead to more retaliatory measures and additional market volatility.

Russia is one of the world's three largest oil producers, meaning any concerted attempt to punish Putin could have a far-reaching effect on the broader crude market. India and China, which have become the key buyers since Moscow's full-scale invasion of Ukraine, would face particular pressure.

Whether tariffs "are merely tough talk or will actually be implemented remains to be seen," said Gao Jian, an analyst at Qisheng Futures Co. "But Russia's oil trade is big in scale, he has to assess and weigh pros and cons."

The OPEC+ producer's crude exports hit a five-month high in March and US sanctions on the nation's oil tanker fleet are showing signs of faltering. Trump told NBC in a phone interview that he would impose penalties if a deal on Ukraine is not reached "and if I think it was Russia's fault."

Trump also said he's considering punishing Tehran with unspecified "secondary tariffs" and raised the threat of bombing Iran until it signs a deal that renounces nuclear weapons.

Brent futures are on track for a slight monthly gain after other US tariffs and sanctions raised concerns over potential disruptions to crude flows, though major traders remain bearish on the outlook for the rest of the year because of rising supply. OPEC+ is due to start reviving idled production next month.

Brent for June settlement was little changed at $72.78 a barrel as of 7:32 a.m. London time after rising as much as 0.5% earlier. The May contract, which expires on Monday, was steady at $73.70 a barrel.

WTI for May delivery was little changed at $69.35 a barrel.

Source: Bloomberg