By Gram Slattery and Nandita Bose

RIYADH/WASHINGTON (Reuters) -Four years ago, Saudi Crown Prince Mohammed bin Salman struggled to get an audience with then-President Joe Biden, who said he wanted to make the Gulf country a pariah after its leader allegedly ordered the murder of a Washington-based journalist.

On Tuesday, President Donald Trump lavished effusive praise on Saudi's de facto ruler, calling him "an incredible man" and a "great guy," and made no mention of human rights concerns in the country.

"I like him a lot. I like him too much," Trump gushed as cameras flashed and the crowd applauded at an investment summit in Riyadh, where the U.S. president kicked off the first major overseas trip of his second term.

The display of affection for a leader with a contentious history mirrored Trump's first term, when he forged an alliance with bin Salman that deepened through years of mutual flattery and dealmaking.

The relationship remains anchored in shared interests: Trump is chasing major economic wins and a revived U.S. role in the region, while bin Salman seeks access to advanced technology, military support and a powerful ally in his push to modernize Saudi Arabia and assert regional leadership.

At the summit, Trump touted a $142 billion defense agreement and a sweeping $600 billion Saudi investment package spanning artificial intelligence, infrastructure and energy.

Trump's ties with the crown prince have sparked criticism from U.S. lawmakers, human rights groups and foreign policy analysts for what they viewed as prioritizing economic interests over human rights.

While bin Salman has denied involvement in journalist Jamal Khashoggi's murder and pointed to reforms such as expanding women's rights as evidence of progress, analysts said these changes were undercut by continued crackdowns on dissent and political freedoms.

Trump's rapport with bin Salman is far warmer than his White House predecessor's. Yet Biden's relationship with the Saudi leader took a friendlier turn too, evolving from initial harsh criticism to pragmatic cordiality.

BIDEN OPTS FOR RESET

In 2019, the Democratic president promised to make Saudi Arabia a "pariah" on the world stage for Khashoggi's killing and its broader human rights record.

But geopolitical realities such as skyrocketing oil prices caused in part by Russia's invasion of Ukraine in 2022 highlighted a need for cooperation between Washington and Riyadh.

That led Biden to decide it was time to reset the strategic relationship, and he eventually visited the crown prince in July 2022.

The two men greeted each other with a fist bump, which drew some criticism as an overly friendly gesture given human rights concerns. White House aides insisted it was a way to lower Biden's risk of contracting COVID-19.

Relations improved quickly as his administration worked to broker a deal for normalizing Saudi-Israeli relations in exchange for a broader U.S. defense agreement. The effort was frozen by the October 7, 2023 attack by Hamas on Israel and Israel's subsequent war on Gaza.

During Trump's visit on Tuesday, the crown prince personally greeted the U.S. president, escorting him up an escalator and later driving him in a golf cart ahead of a state dinner.

In a moment that underscored the depth of their personal bond, Trump pledged to lift U.S. sanctions on Syria - a dramatic move that he said came at bin Salman's request.

"Oh, what I do for the crown prince," Trump said, as the crown prince placed his hands over his heart and led a standing ovation.

(Reporting by Gram Slattery in Riyadh and Nandita Bose in Washington, Additional reporting by Andrea Shalal, Writing by Nandita Bose; Editing by Colleen Jenkins and Cynthia Osterman)