President Barack Obama will play diplomat next week during a global swing, underscoring one special relationship and navigating an increasingly awkward one.  

The trip will provide a reminder that the United Kingdom remains America’s closest ally. It will also highlight Germany’s standing as a European power. But it will also provide the latest illustration of how another longtime ally, Saudi Arabia, continues to drift from Washington’s orbit on key issues.  

From oil prices to the fight against the Islamic State to dealing with Iran, the strains to the U.S.-Saudi relationship are plenty.  

White House officials have been critical of Saudi leaders and the heads of other Sunni Muslim countries, urging them to do more to confront the Islamic State, also known as ISIS.  

“We do hope that we and the [Gulf Cooperation Council] will be able to do more in the fight against the terrorist threat and work in even greater partnership on that,” Robert Malley, a senior adviser to the president for countering ISIS, told reporters Thursday.  

The Gulf Cooperation Council includes Saudi Arabia and the Persian Gulf states of Bahrain, Kuwait, Oman, Qatar and the United Arab Emirates.  

Virginia Democratic Sen. Tim Kaine, a member of the Foreign Relations and Armed Services committees, said U.S. officials “want them to be all in on ISIS” but instead “we don’t see an urgency on their part.”  

And the frustration cuts both ways, with Saudi officials and their Sunni allies wondering why Obama has taken a more hands-off approach to the Middle East than many of his predecessors.  

Obama heads to Saudi Arabia for a private meeting Wednesday with the Saudi leader, King Salman bin Abdulaziz Al Saud.  

Obama, Salman and the other GCC leaders will then hold three distinct sessions. There will be one on ISIS and al-Qaida, and another on general regional stability.  

But there also will be one on a more touchy issue for the Sunni leaders: “Iran and regional security and our efforts to prevent destabilizing actions across the region,” was how Ben Rhodes, deputy White House national security adviser, put it Thursday.  

There will be disagreements and calls to strengthen joint efforts on all three issues. But lawmakers and analysts agree that Obama will hear one overarching message from the Sunni leaders about fighting ISIS in Syria — and a list of other Middle East security matters.  

“They’re looking for the U.S. to lead an effort and they’ll join in,” Senate Foreign Relations Chairman Bob Corker, R-Tenn., said. “At the end of the day, what they communicate directly to us when they come here, they’re looking for the U.S. to do more.”  

But Corker, no ally of the White House on many foreign policy matters, inadvertently highlighted the difficult task facing Obama when he summed up the actions of Saudi Arabia and other Sunni countries on ISIS and other issues: “So far, all talk.”  

Christopher Preble, a defense analyst at the Cato Institute, said that on many issues “U.S. interests and Saudi interests don’t align.”  

“Obama won’t be this direct, but if the message from the Saudis is they feel increasingly discomforted with the reality that those interests don’t line up more and more often, then he might respond, ‘That’s tough,’” Preble said.  

That message would be carried out behind closed doors. Publicly, expect Obama and his Sunni counterparts to highlight the issues on which they agree.  

“You’ll hear more coming out of the summit. There’s been agreements reached to increase our cooperation on counterterrorism, streamlining the transfer of critical defense capabilities to our GCC partners, bolstering the GCC’s ballistic defense missile defense system, and defending against the cyber threats,” Malley said  

“On all of those, I think, you’ll see progress has been made,” he added. “There’s been much deeper cooperation between us and the GCC.”  

Arms sales have long been a part of America’s dealings with the Saudis and other Sunni countries. To that end, Corker said many lawmakers want Obama, while in the region, to announce that he is green-lighting deals with Qatar and Kuwait.  

Also hanging over the summit, Preble said, is a sense that the Sunni leaders are trying to wait out Obama. Since he has only 10 months left in office, some allies in the region appear willing to gamble that the next U.S. commander in chief will send American ground forces to fight ISIS and bring stability to Syria and Iraq.  

“I think that would be very foolish,” Kaine said. “It’s a threat in their region and we’re waiting to see how much they’ll stand up against it.”  

But lawmakers and experts agreed that the president was unlikely to secure any such commitments next week.  

“He’s irrelevant in the region,” Arizona Sen. John McCain, chairman of the Armed Services Committee and Obama’s 2008 general election foe, said this week. “He has zero credibility there.”  

Contact Bennett at johnbennett@cqrollcall.com. Follow him on Twitter @BennettJohnT.

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