(Bloomberg) -- Vladimir Putin has everything to gain from his first summit on Monday with Donald Trump. The U.S. president’s critics as well as American allies are worried the Russian leader will get what he wants.

Trump and Putin will sit down together in Helsinki for a day of meetings that U.S. and Russian officials say will touch on every major point of tension between their countries -- the Kremlin’s meddling in the 2016 election, its military incursions into Ukraine and Syria, Moscow’s saber-rattling toward NATO allies and the American economic sanctions intended to punish Russia for its behavior.

For Putin, it’s a win just to meet one-on-one with the U.S. leader, whose campaign is under investigation back home over whether Trump associates colluded with the Kremlin effort to help get Trump elected. The upside for Trump is less clear -- and that worries some lawmakers and foreign policy experts in Washington.

“If the White House is as confused about the nature of the threat we face from Mr. Putin as it seems to be, a meeting between the Russian President and his counterpart could not be more concerning,” Senator Jeff Flake, an Arizona Republican, said in a speech on the chamber’s floor Thursday. He called “admiration” Trump has shown for Putin “unconscionable.”

Senator John McCain, also an Arizona Republican, said Trump “must show he can be strong and tough with Vladimir Putin.”

Trump indicated on Thursday that he doesn’t have a list of demands for the Russian president.

“We go into that meeting not looking for so much,” he told reporters at a news conference following a NATO summit in Brussels. “We want to find out about Syria. And we will, of course, ask your favorite question about meddling. I will be asking that question again. But we’ll also be talking about other things. We’ll be talking about Ukraine.”

NATO Tensions

Ahead of the Helsinki meeting, Trump upended the NATO summit by demanding that America’s closest allies more rapidly increase their defense spending, insinuating the U.S. might withdraw from the bloc otherwise.

He declared that it was German Chancellor Angela Merkel, not him, who was beholden to Putin because of a pipeline system Russia is expanding between their countries. He left open the possibility of recognizing Moscow’s 2014 annexation of Crimea from Ukraine. Though Trump declared that NATO was stronger thanks to his behavior and reaffirmed the U.S. commitment to the alliance, the Brussels summit could hardly have gone better for the Kremlin, which has long sought to exploit and widen cracks among Western nations.

The Pipeline That Pits Trump Against Merkel and Putin: QuickTake

Trump’s remarks about Merkel drew a rare, pointed rebuke from the chancellor, whose relationship with Trump has been strained from the start, as well as from the House and Senate Democratic leaders, Nancy Pelosi and Chuck Schumer.

“His behavior this morning is another profoundly disturbing signal that the president is more loyal to President Putin than to our NATO allies,” Pelosi and Schumer said in a joint statement. “If the president leaves the Putin meeting without ironclad assurances and concrete steps toward a full cessation of Russian attacks on our democracy, this meeting will not only be a failure – it will be a grave step backward for the future of the international order and global security.”

Trump said he anticipates Putin will again deny any Kremlin interference in the election. Indeed, the Kremlin is preparing to respond in a manner that doesn’t undercut Trump while also reiterating Putin’s denials, according to a senior Russian official. The person asked not to be identified discussing Moscow’s outlook ahead of the summit.

Nuclear Deal

Kremlin and White House officials maintain there’s much to be gained on both sides from the summit. One possibility is a new nuclear weapons agreement. The New START treaty negotiated under former President Barack Obama will expire in 2021, and both sides would like to extend and possibly expand the accord. The Russian and American leaders are also likely to discuss how to resolve a dispute over compliance with a 1987 treaty that bans the deployment of intermediate-range missiles on land.

“What would be the ultimate?” Trump said in Brussels. “Well, let’s see. No more nuclear weapons anywhere in the world would be the ultimate, OK? No more wars, no more problems, no more conflict. Let’s find a cure to every disease known to mankind or womankind.”

Putin meanwhile is stepping up efforts to broker a deal for pro-Iranian militias in Syria to withdraw from areas near the border with Israel in favor of government troops. The move could be a way to ease tensions with the U.S. as well as shore up Putin’s ally, Syrian leader Bashar al-Assad.

Read more: Putin Steps Up Effort to Broker Syria Deal Ahead of Trump Summit

Most of all, the Helsinki summit provides Trump yet another live trial of his sincere belief that he’s uniquely qualified to build relationships and negotiate difficult deals with American adversaries. As with North Korea’s leader Kim Jong Un, whom Trump met in Singapore in June, the president believes he can generate broad and unprecedented cooperation between the U.S. and Russia despite seemingly intractable differences.

“If you can imagine what reduced tension could do in the case of U.S.-Russia and Europe-Russia, it would be on a much bigger scale,” the U.S. ambassador to Russia, Jon Huntsman, told reporters on a call previewing the meeting last week. “So I wouldn’t underplay at all the importance of actually sitting down for the first time in a meeting-summit environment and discussing the issues that really matter most.”

That sentiment is shared by the Kremlin. The senior Russian official said both sides were determined to find areas of agreement and that the summit could lay the groundwork for future steps.

But it isn’t clear whether Trump’s desire to reconcile with Putin is driven by a strategic vision or simply by his penchant for contrarian governance.

“It reflects the way Trump and certainly some of the people in his orbit view things,” Jeff Mankoff, deputy director of the Washington-based Center for Strategic and International Studies’ Russia and Eurasia Program, said in a phone interview. “‘People are telling me I can’t have this meeting, everybody’s saying Russia is the problem - well, I don’t think Russia is the problem. I’m going to show everybody.”’

To contact the reporters on this story: Margaret Talev in Washington at mtalev@bloomberg.net;Justin Sink in Washington at jsink1@bloomberg.net;Henry Meyer in Moscow at hmeyer4@bloomberg.net

To contact the editors responsible for this story: Alex Wayne at awayne3@bloomberg.net, Mike Dorning

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