The Washington Post reported on Friday that Moscow had passed sensitive intelligence to Tehran, including the locations of US warships and aircraft in the region.

But Washington has taken a restrained tone in response so far, with Trump saying President Vladimir Putin wanted to be "helpful" on the Middle East in a call on Monday, even as Putin offered "unwavering support" to Iran's new supreme leader.

Washington has also halted sanctions on some Russian oil as crude prices spiked because of the Iran war. The sanctions were originally imposed to cut Russia's funds for its war on Ukraine.

"The president and his special envoy (Steve) Witkoff have both said that, of course, they've sent a message to Russia that if that was taking place, it's not something they would be happy with and they hope that it is not taking place," White House Press Secretary Karoline Leavitt told a briefing.

Witkoff, a businessman who has led US talks with both Russia and Iran in recent months, said Russia should be taken at its word when it denied sharing intelligence with Tehran.

"I'm not an intel officer, so I can't tell you," Witkoff told CNBC when asked if the Russians had shared intel, and why Washington would still waive some sanctions on Moscow if so.

"I can tell you that yesterday on the call with the president, the Russians said that they have not been sharing. That's what they said. So, we can take them at their word."

The White House said that Trump's decision to waive sanctions on sales of Russian oil to India in particular was because New Delhi had previously complied with US sanctions.

"As we work to appease this temporary gap of oil supply around the world because of Iranians, we have temporarily permitted them to accept that Russian oil," Leavitt said.

"This short-term measure, we don't believe it will provide significant financial benefit to the Russian government at this time."

Trump has faced scrutiny throughout both his terms as president for his friendly relations with Putin, particularly since the Russian leader ordered the invasion of Ukraine.

The US president insists that he alone can persuade Putin to make a deal on Ukraine, even if his earlier boasts that he could do so within 24 hours of taking office have proven fruitless.

"We had a very good talk, and he wants to be very constructive," Trump said on Monday.