Signs of US-Saudi rift after rare state department criticism of Mohammed bin Salman's foreign policy

More signs of a growing rift between the US state department and Saudi Arabia emerged on Friday, as chief Rex Tillerson offered new criticism of Crown Prince Mohammed bin Salman's foreign policy.

Tillerson singled out the Saudi-led war on Yemen, its blockade on Gulf neighbour Qatar, and Riyadh's alleged coercion of Lebanon Prime Minister Saad Hariri for mild - but rare - criticism on Friday.

"With respect to Saudi Arabia's engagement with Qatar, how they're handling the Yemen war that they're engaged in, the Lebanon situation, we would encourage them to be a bit more measured and a bit more thoughtful in those actions to, I think, fully consider the consequences," Tillerson said, speaking from Paris.

He also called for a "complete end" to the Saudi-led blockade on Yemen.

It follows a statement by President Donald Trump on Wednesday urging Riyadh to life its crippling siege on Yemen.

"[I] request that they completely allow food, fuel, water, and medicine to reach the Yemeni people who desperately need it. This must be done for humanitarian reasons immediately," he said in a statement.

Saudi Arabia tightened its blockade on Yemen following after rebels fired a missile at the capital Riyadh last month.

Human rights groups and NGOs have warned the siege threatens to worsen the already dire humanitarian situation in the country and lead to more deaths from starvation and disease.

Saudi Arabia appears to have ignored this request and intensified its bombing of Yemen, hitting a rebel-controlled TV station on Saturday.

Tillerson and the state department have been forthright in their criticism of Saudi foreign policy and concerned by the close relationship between Crown Prince Mohammed bin Salman and Trump aide and son-on-law Jared Kushner.

He called for dialogue when a Saudi-led blockade on Qatar was launched in June, while Trump appeared to back the measure.

Yet, Saudi Arabia was likely embarrassed and angered by Trump's announcement this week that the US embassy will move to Jerusalem.

This followed talk that Saudi Arabia was backing US efforts to find a peace deal between the Palestinians and Israelis and rumours that Riyadh had opened talks with Israel.

The US offers some intelligence and refuelling support to the Saudi-led coalition but is not directly involved in military engagements.

Saudi Arabia has been one of Washington's closest allies in the region but Riyadh now appears to be strengthening ties with Russia.