(CNN) As Gen. Joseph Dunford, the chairman of the Joint Chiefs of Staff, descended into Baghdad on Monday, the highest-profile passenger aboard his military aircraft was neither a seasoned Iraq hand nor even someone who'd visited the country before.

It was Jared Kushner, the 36-year-old commercial real estate magnate, whose marriage to President Donald Trump's eldest daughter has thrust the otherwise inexperienced diplomat into the center of US foreign relations -- and seemingly every top issue facing the administration.

Kushner was visiting Iraq at Dunford's invitation to receive briefings on the military campaign against ISIS, and planned to meet with US and Iraqi officials. Iraq is now the latest portfolio handed to Kushner, whose role as Trump's senior adviser appears to be growing by the day, and whose influence over his father-in-law now extends into nearly every area of government.

In some instances, Kushner's involvement in his father-in-law's administration has raised ethical questions, given the vast property and business holdings Kushner managed in his time running his family's real estate empire. His ties to Russia during the presidential transition have also drawn scrutiny, and he's due to answer questions from Senate investigators soon.

"I said, 'Hey, next time I go to Iraq, if you're interested, come and it'd be good,' " Dunford told reporters on the flight to Iraq, according to Reuters . He said he'd invited Kushner weeks ago.

Multiple White House and administration officials say Kushner has now eclipsed nearly all of Trump's West Wing and Cabinet advisers in terms of influence, establishing himself as the key envoy for those outside the administration -- including foreign diplomats, business executives and even some members of Congress -- to direct their bidding. He's also, by the way, running a government reform effort and spearheading criminal justice reform.

The elevated position has caused some annoyance at the agencies and departments more typically tasked with carrying out American foreign policy. One ally of Secretary of State Rex Tillerson described the top diplomat as frustrated with Kushner's diplomatic exploits. Officials said Tillerson intervened last month to delay a White House meeting with top Saudi officials over a plan to combat ISIS because he felt there was not enough planning for it.

Other allies and aides deny any tension between the two men and say Kushner has been very helpful both in getting the secretary's input and focusing the President's attention on issues important to Tillerson.

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Speaking Monday, White House press secretary Sean Spicer said Kushner was working jointly with the State Department to manage the administration's foreign affairs.

"There's a lot of relationships that Jared's made over time -- Mexico being one of them -- that are going to continue having conversations with him," Spicer said. "That doesn't mean by any means it's being done without the coordination with the State Department. It's quite, in fact, the opposite. He's continuing to work with them and facilitate an outcome. But he brings a perspective to this, and began doing that during the transition. But again, it's not a binary choice where he's doing this at the expense of somebody else."

During last year's presidential campaign, and later during the transition, Kushner was identified by Trump's team as the principal point of contact for foreign governments looking to either congratulate the new US leader or begin diplomatic talks.

The role has gained Kushner scrutiny in recent weeks when it was revealed he met with the Russian ambassador to Washington, Sergey Kislyak, as well as the head of a Russia state-owned bank, Sergey Gorkov, in December . According to a source familiar with what transpired, Kushner's interactions with Russians during the transition as a point man "looking for the right person to engage with on Russia," further reflection of his elevated status within Trump's sphere.

Senate investigators are planning to question Kushner about the meetings as part of a larger probe into Russia's influence in last year's contest.

As Trump enters his eleventh week in office, Kushner's role has expanded to include a globe-spanning collection of foreign assignments -- North America, the Middle East and China included. Even as Senate-confirmed foreign policy aides work to cement their influence within the administration and in foreign capitals, Kushner's already established role has grown to include duties typically assigned to a national security adviser or even a secretary of state.

Before his surprise trip to Iraq, Kushner had been preparing intensively for Thursday and Friday's meeting with Chinese President Xi Jinping , which will take place at Trump's Mar-a-Lago estate in Florida. Kushner has acted as a key conduit between the Chinese government and the White House in the lead-up to the two leaders' talks, which Xi's representatives requested take place at Trump's Florida estate.

In discussions with China's ambassador in Washington, Kushner has sketched the agenda for the meetings and dictated some elements of the Palm Beach summit, according to people familiar with the planning.

Kushner is seen as a moderating voice on US-China ties, which are becoming both more complicated and more vital as Trump begins his presidency. His daughter, Arabella, has played an unlikely role as well in softening Trump's approach; video of the five-year-old presidential granddaughter singing in Chinese at a New Year's celebration in Washington went viral in China.

Arabella singing a song she learned for #ChineseNewYear. Wishing everyone an amazing year to come during these days of celebration. 新年快乐！ A post shared by Ivanka Trump (@ivankatrump) on Feb 2, 2017 at 4:30am PST

But Kushner's close involvement in planning the Chinese visit has also raised ethical questions. His family's real estate company was recently in talks with China's Anbang Insurance Group to redevelop a flagship property in Manhattan; the talks were recently called off after scrutiny from ethics watchdogs and Democratic lawmakers.

Disclosure reports released by the White House Friday showed Kushner, along with his wife Ivanka Trump, could be worth more than $700 million. At one point he held a position in 267 separate entities, ranging from the Trump transition team to dozens of property holdings in New York and New Jersey, meaning more potential conflicts are likely to arise, even after Kushner has resigned from his business positions.

His expansive responsibilities don't end at foreign affairs. Last week the White House announced Kushner would lead a presidential office tasked with reshaping the federal bureaucracy. He's preparing to meet with lawmakers to discuss criminal justice reform. And he's taken part in discussions to improve the Department of Veterans Affairs and tackle the nation's opioid abuse epidemic.

As Kushner list of responsibilities grows, the limitations on his time are also becoming evident. As he traveled to Iraq Monday, Trump was preparing to welcome Egyptian President Abdel Fattah el-Sisi at the White House for talks, a session Kushner would likely have attended if he wasn't overseas on another assignment.

White House officials said the meeting was likely to include a discussion of Middle East peace, another area Trump has charged Kushner with overseeing. Kushner, an observant Jew, has known Israeli Prime Minister Benjamin Netanyahu for decades, and Trump has expressed rampant optimism at his son-in-law's ability to broker an agreement.

So, too, has Trump lent his support to Kushner's attempts at managing friendlier ties with Mexico, even as the President continues his controversial plan to construct a border wall.

The U.S. has a 60 billion dollar trade deficit with Mexico. It has been a one-sided deal from the beginning of NAFTA with massive numbers... — Donald J. Trump (@realDonaldTrump) January 26, 2017

of jobs and companies lost. If Mexico is unwilling to pay for the badly needed wall, then it would be better to cancel the upcoming meeting. — Donald J. Trump (@realDonaldTrump) January 26, 2017

The two men at times have seemed at odds; in February, as Kushner was meeting with Mexican officials in Washington to arrange a visit by President Enrique Peña Nieto, Trump tweeted: "If Mexico is unwilling to pay for the badly needed wall, then it would be better to cancel the upcoming meeting."

Peña Nieto ended up canceling his visit.