WASHINGTON — Qatar may score an important victory on Tuesday if President Trump, as expected, tells the leader of the tiny Persian Gulf nation that he now views Qatar’s rivals as stonewalling a solution to an important regional dispute.

Mr. Trump will host Emir Tamim bin Hamad Al-Thani at the White House, shifting from describing Qatar as a “funder of terror” to what a senior administration official on Monday said was sympathy with Doha’s continued struggle under a four-nation embargo led by Saudi Arabia and the United Arab Emirates that was imposed in June.

With urgent conflicts piling up across the Middle East, Mr. Trump is eager to resolve the Sunni Muslim regional feud as he considers the imminent prospect of launching a punishing military strike in Syria over a suspected chemical weapons attack. Qatar is host to al-Udeid Air Base, which is home to nearly 10,000 American troops and is the overseas headquarters for United States Central Command that would launch any strike against Syria.

Over the past year, the emir has spent millions of dollars hiring lobbyists and flying influential American power brokers to Qatar in a charm offensive to win over the Trump administration — and deflate his rivals’ efforts to dethrone him. Riyadh and Abu Dhabi have accused Doha of financing terrorism, cozying up to Iran and harboring fugitives, and the embargo forced changes to airplane routes and severed Qatar’s only land border.

It has also troubled American forces and strategy in the region, which envisions a united Arab effort to combat terrorism and contain Iran.

Former Secretary of State Rex W. Tillerson spent months trying to mediate the dispute, eventually siding with Qatar. But until recently, Mr. Trump remained unconvinced — and Mr. Tillerson washed his hands of the issue because of the president’s intransigence, top officials said at the time.

Still, Qatar has signed agreements with the United States for sharing information on terrorists and terrorist financing. And on Monday, the State Department notified Congress that it had approved the potential sale of $300 million in advanced rocket systems to Qatar, which a statement called “an important force for political stability and economic progress in the Persian Gulf region.”

In the meantime, a trove of hacked emails of those working on behalf of the United Arab Emirates has tarnished Abu Dhabi’s and Riyadh’s claims. And just recently, Qatar added to its already formidable roster of Washington lobbyists by retaining Brian Ballard, a top fund-raiser for Mr. Trump.

Now, the administration official said, Mr. Trump believes the holdout against settling the embargo is not Qatar but the United Arab Emirates and its crown prince, Mohammed bin Zayed. And Mr. Trump is pushing for a settlement because the dispute suddenly seems to be an unneeded distraction in a region roiled by conflict, said the official, who was not authorized to discuss the sensitive diplomatic issue publicly.

Last week, Mr. Trump announced that he would be pulling American forces out of Syria almost immediately, despite a previous declaration that troops would be there indefinitely. Advisers persuaded the president to delay the withdrawal for a few months. By Monday, he was hinting at a sudden escalation of force after another suspected chemical attack in Syria by its leader, President Bashar al-Assad.

“We are meeting with our military and everybody else, and we’ll be making some major decisions over the next 24 to 48 hours,” Mr. Trump said on Monday morning. A chemical attack, he said, “can’t be allowed to happen.”

Confusion over the Trump administration’s regional policy goals has led a caravan of Middle Eastern leaders to come to Washington to lobby directly for their interests. Three weeks ago, Crown Prince Mohammed bin Salman of Saudi Arabia was hosted at the White House and then toured the United States; he headed home this past weekend, after a reunion with Presidents George Bush and George W. Bush.

Now, Mr. Al-Thani will get his moment.

“The visit of His Highness will showcase the strength and honesty that exists between the U.S. and Qatar,” said Jassim Al-Thani, a spokesman for Qatar’s embassy in Washington.

The Trump administration had hoped to bring all of the leaders of the Gulf Cooperation Council together for a summit meeting in Washington this month. But Prince Mohammed of Saudi Arabia and leaders of the United Arab Emirates said they would decline such an invitation were it issued, since such a meeting would have required an end to their Qatar embargo, senior administration officials said.

Jon B. Alterman, a senior vice president at the Center for Strategic and International Studies, said the growing disarray in the Middle East was in some ways reflected and grows out of a chaotic White House.

“How do you pursue a coordinated interagency U.S. government strategy when the U.S. government isn’t coordinating?” Mr. Alterman asked, citing the absence of ambassadors in Saudi Arabia, the Emirates and Qatar and dozens of other countries along with vacancies in Washington.

“This is precisely the kind of thing where you need a process to make decisions, and this administration has a really hard time with processes.”

The dispute between the Emiratis and Qataris has become remarkably nasty, with each side accusing the other of computer hacking — with some resulting revelations that have embarrassed the White House.

Last week, Federal District Judge Ketanji Brown Jackson ruled in Washington that a plausible case existed that the Emirates hacked the email accounts of Farhad Azima, an international businessman, for information to assault his character.

In a separate lawsuit in California, Federal District Judge John Walter refused to order Qatar to stop disseminating emails and other documents from Elliott Broidy, a top Republican fund-raiser and a contractor for the Emiratis. The judge concluded that Mr. Broidy lacked evidence of Qatar’s involvement.

Both rulings were wins for the Qataris.

Mr. Broidy’s emails revealed a concerted campaign by Saudi Arabia and the U.A.E. to use billions of dollars to gain influence inside the White House. Those efforts have attracted the interest of Robert S. Mueller III, the special counsel investigating Russia’s interference in the 2016 election.

“People don’t understand how seriously Qatar is taking this issue,” said Mr. Al-Thani, the Qatari Embassy spokesman. “We are upping our game to protect our sovereignty and independence.”