HELSINKI — The whole world is watching now.

As President Donald Trump and Russian President Vladimir Putin sit down for their first summit here today— one 90-minute meeting with no one else in the room followed by one featuring the two leaders and top aides — the unresolved issues involving the two sides range from nuclear nonproliferation to the balance of power in Europe and election-meddling.

The public glimpse into their talks will come at a joint press conference set for 9:50 a.m. ET.

But there is no real set agenda for the hastily arranged power chats, which were announced less than three weeks ago and for which Trump has declined to elaborate on any goals beyond simply meeting with Putin and raising the issues at hand.

Trump said little about his meeting with Putin when asked about his goals during a breakfast Monday with Finnish officials.

"We’ll see him in a little while," Trump said. "We’ll do just fine."

With any deal-making to be done on the fly, some American experts on Russia are deeply concerned that gives Putin, who has been in power in Moscow for the last 18 years, the upper hand over Trump.

"He knows the details of these issues way better than Trump, or indeed almost any other head of state in the world," Michael McFaul, who served as President Barack Obama's ambassador to Moscow, wrote in the Washington Post. "That’s why the extended one-on-one meeting with Trump planned for the summit gives Putin a huge advantage."

On two of the most pressing matters, Russia's cyber attacks against the U.S. and Putin's incursions into Ukraine, Trump has signaled repeatedly that he is not nearly as worried about them as officials in his own administration, Democrats and Republicans in Congress, and much of the American public are.

"I will absolutely bring up meddling," Trump said at a press conference with British Prime Minister Theresa May last week. But, knowing at the time that his Justice Department was about to announce indictments against a dozen Russian spies for cyber attacks against Democrats during the 2016 campaign, he referred to the investigation into his campaign's ties to Moscow as a "rigged witch hunt."

While U.S. officials say they will maintain sanctions against Russia for seizing Crimea from Ukraine in 2014, Trump himself hasn't ruled out recognizing that annexation of territory that Putin believes is rightfully his.

"We’re going to have to see," Trump told reporters on Air Force One late last month.

Anna-Liisa Heusala, a Russian Studies professor at the University of Helsinki, said Putin wants "actual recognition or de facto acceptance" of his military action in Ukraine, Syria and other regional hotspots and affirmation of his view of Russia as a "superpower, above international norms and law."

"From Russia’s perspective, its actions in Ukraine and the Crimea, which it partially justified with humanitarian causes, were a demonstration of its strengthened role and ability to set boundaries for the actions of other parties when these are deemed to seriously threaten Russian national interests," she said.

"As Russia categorically opposes the expansion of NATO near its border, it interprets that the annexing of the Crimea was also a defensive action due to the military importance of the area."

Concerns about the Russian leader's acumen, and the possibility of Trump faltering, cross the political spectrum.

Luke Coffey, director of the foreign policy center at the conservative Heritage Foundation in Washington, wrote that Trump has an opportunity to stand strong with NATO and "press Putin" on Ukraine, Moscow's backing of the regimes in Iran and Syria and attacks on elections in democratic nations.

"President Trump should go into this summit with his eyes wide open," Coffey wrote. "Since coming to power in 1999, Putin has never shown that he can be a trusted partner of the United States. At almost every opportunity, he has pursued policies that undermine America’s national interests and those of its closest partners."

Some veteran American foreign policy hands say that it is worthwhile for the U.S. to re-engage with Russia after years of deterioration in the relationship, several failed attempts to jump-start it and the resumption of an arms race between the two countries.

But there is also fear, amid the Russia investigation that has dogged Trump at home and boiling tension over NATO's eastward expansion and Putin's push to influence his western neighbors, that the one-on-one meeting could end up harming U.S. interests.

"I’m shaking my head so violently I have whiplash," said Ellen Tauscher, who was undersecretary of State for arms control and international security during most of Obama's first term.