Mohammed bin Salman welcomed at White House by Donald Trump

Saudi Crown Prince Mohammed bin Salman began his 20-day visit to the United States with a three-hour meeting with President Donald Trump that addressed their shared concerns over Iran and also investments of billions of dollars.

Both leaders stressed the strength and potential of Saudi-US ties before sitting down for talks with their officials.

Sitting side by side in the Oval Office, Mr Trump hailed his personal friendship with Crown Prince Mohammed and the improved relations with Saudi Arabia forged under his administration.

“We became very good friends over a very short period of time” President Trump said, noting the “great friendship, the great relationship” now, in contrast with “very strained [relations] during the Obama administration”.

Mr Trump displayed cue cards showing Saudi military purchases from the US at more than US$12.5 billion (46bn) as he touted investments and economic co-operation with the Kingdom. “We are bringing back hundreds of millions of dollars into the United States... over 40,000 jobs” he said.

Crown Prince Mohammed, speaking in English, described the Kingdom as “the oldest ally of America in the Middle East”, with political, economic and security co-operation as deep foundations for the relationship.

“We know today the relation produced more than four million jobs directly and indirectly,” he said.

The Saudi pledge for $200bn in investments would rise to $400bn when fully implemented, said the crown prince, and that a 10-year window to implement the deal was already in place.

"This is a signal that there are a lot of things that could be tackled in the close future and more opportunities. And that’s why we are here today, to be sure that we’ve tackled all the opportunities and achieve it and also get rid of all the threats facing both our countries."

On foreign policy, Mr Trump said: "We are working seriously with to stop the financing of terrorism."

Asked about the Iran nuclear deal, he said: "We're going to see what happens, the Iran deal is coming up. You're going to see what I do. But Iran has not been treating that part of the world well... we will talk about that today."

Mr Trump also referred to a visit later this year by Saudi Arabia's King Salman.

“I miss your father, special man, and I know he’s coming over soon,” Mr Trump told his visitor.

Crown Prince Mohammed's visit to the Oval Office, his first in this role, was followed by a lunch attended by Vice President Mike Pence, National Security Adviser HR McMaster and Energy Secretary Rick Perry. The Saudi Ambassador to the US, Prince Khalid bin Salman, Minister of State Musaed Al Aiban, and Minister of Commerce Majid Al Qasabi were also in attendance.

White House economic adviser Gary Cohn, the president's son-in-law and advisor Jared Kushner and White House Chief of Staff John Kelly were also present.

Ahead of meeting Mr Trump, Crown Prince Mohammed went to Congress and met Senators Bob Corker, Mitch McConnell, Chuck Schumer and House Speaker Paul Ryan. The discussions touched upon the war in Yemen ahead of a vote on a senate bill later on Tuesday that would require any US forces not involved in fighting Al Qaeda to leave the country within 30 days. The bill, sponsored by senator Bernie Sanders, was not expected to get the 51 votes required to put it up for a floor vote. Instead it's more likely to be tabled.

The Saudi Crown Prince was also due to attend a working dinner to discuss the Middle East peace process with Mr Kushner, peace envoy Jason Greenblatt, and Gulf co-ordinator at the White House Michael Bell.

Vice President Pence will host Crown Prince Mohammed for dinner on Wednesday and he is expected to also meet Defence Secretary James Mattis and CIA director Mike Pompeo.

Nuclear energy co-operation is high on the Saudi agenda. Energy Secretary Perry, who met a Saudi delegation in London last month, has already initiated talks on helping Riyadh acquire technology to build its own nuclear reactors.

Saudi foreign minister Adel Al Jubeir said on Monday that "discussions with the United States as well as other countries" are under way. He named Russia, China, France, South Korea and possibly Japan among those that his government is assessing with possible co-operation.