"I am proud to announce that Massad Boulos will serve as Senior Advisor to the President on Arab and Middle Eastern affairs," Trump posted on Truth Social of the appointment, which puts his daughter Tiffany's father-in-law in a major White House position.

Boulos was a key emissary for the Trump campaign, helping to mobilize Arab American and Muslim voters, many of whom were angry over President Joe Biden's steadfast support for Israel in the Gaza war even as the civilian death toll rose into the tens of thousands.

The businessman will take over a difficult portfolio, with Israel's war still raging in Gaza, a fragile ceasefire between Israel and Hezbollah in Lebanon seeing early violations, and rebel forces in Syria making advances against the government of Bashar al-Assad.

Boulos's son, Michael, is married to Trump's daughter Tiffany. 

On Saturday, Trump named real estate executive Charles Kushner -- the father of his son-in-law Jared -- as his pick to be the US ambassador to France, the latest case of Trump eschewing experience or expertise as the criterion for joining his team.

"Massad is an accomplished lawyer and a highly respected leader in the business world, with extensive experience on the International scene," said Trump of his appointment to the Middle East advisor job. 

"He has been a longtime proponent of Republican and Conservative values, an asset to my Campaign, and was instrumental in building tremendous new coalitions with the Arab American Community."

The Republican referred to Boulos as "a dealmaker."

Trump often promised on the campaign trail to bring a swift end to the wars in Gaza, Ukraine and elsewhere, without specifying how he would do so. 

Speaking to UK-based broadcaster Sky News in October, Boulos said it was important to finish the war "quickly."

"What do we mean by finishing it quickly is, I mean, you have some military targets that you have to accomplish, which is to get rid of the Hamas infrastructure and ability to launch new attacks and so on," he said.

"Let's move to peace, and let's move to rebuilding Gaza and rebuilding Lebanon," he added. 

"We want Gaza to be prosperous. We want the Palestinian people to be prosperous, to live in peace, to live in harmony, side by side with the Israelis and full security on both sides."

Boulos's family operates at least two automotive parts distribution companies in Nigeria.

The businessman, a member of the Christian Maronite community, has in the past run in vain for a seat in the Lebanese parliament.

Trump has come under fire for a series of controversial picks for important posts in his incoming White House administration.

His choices have shown a pattern, so far, of selecting people, often wealthy, who are close to his family or of proven loyalty -- rather than exhibiting experience or expertise in a given field.

The elder Kushner, who is also a lawyer, served time in a federal prison for tax evasion. Trump pardoned him in 2020 towards the end of his first term.

On Saturday, Trump named loyalist Kash Patel as the next director of the Federal Bureau of Investigation (FBI), a move that would replace the agency's current leader before the end of his term.

A fierce defender of the incoming president, Patel supports the Republican hardliner notion of an anti-Trump "deep state" of allegedly biased government bureaucrats working to stifle Trump from behind the scenes, even having written a book on the subject.