– President Donald Trump will speak one-on-one with President Vladimir Putin of Russia this month when they meet in Helsinki, the administration confirmed Thursday, injecting an element of unpredictability and mystery into an encounter that White House advisers describe as a chance to reset a tense relationship.

Jon Huntsman, the U.S. envoy to Moscow, said Trump would use the meeting to “continue to hold Russia accountable for its malign activities,” including Putin’s election meddling and his military incursion into Ukraine. The leaders also are expected to discuss arms control and the conflict in Syria.

But there is no telling what Trump — a president who abhors long briefing papers and often disregards or defies the advice of his advisers — will choose to say while he is alone with Putin, a prospect that puts some of his aides and experienced diplomats inside and outside the government on edge.

“Putin is very clever in giving a distorted and self-serving version of history on some of these substantive issues,” said Alexander Vershbow, a former U.S. ambassador to Russia. “He can charm Trump into changing his position or dropping long-standing U.S. positions if he’s alone with him for too long.”

Such meetings are commonly referred to as one-on-one because no advisers are present, but translators for each leader would be expected to attend.

Huntsman said Trump and his administration were approaching the Putin meeting “with our eyes wide open” — the same phrase they used in the run-up to Trump’s summit meeting in Singapore with Kim Jong Un, the North Korean leader. That session was convened to discuss nuclear disarmament by Pyongyang.

“You can’t solve problems if you’re not talking about them,” Huntsman said Thursday during a briefing for reporters about the meeting. Trump thinks a better relationship between Russia and the United States would be good for both, he said, “but the ball really is in Russia’s court, and the president will continue to hold Russia accountable for its malign activity.”

He said that Trump saw a one-on-one exchange as vital to starting a dialogue with Putin. But Huntsman played down the prospects for any breakthroughs, saying, “The fact that we’re having a summit at this level at this time in history is a deliverable in and of itself.”

Still, there are serious issues to be discussed. Trump is likely to raise the prospect of extending the New Start arms reduction treaty, Huntsman said, and to urge Russia to return to compliance with the Intermediate-Range Nuclear Forces Treaty, after Moscow tested and deployed a cruise missile prohibited under the pact.

Yet Trump’s advisers concede they cannot be certain of what he will choose to say or do.

Huntsman said the United States and Russia have yet to hold the kind of “direct conversations, across-the-table conversations — about things like election meddling and malign activity — that really do need to take place.” But he said it would be up to Trump to choose how he wished to broach those topics with Putin.

The Trump administration overall has been far tougher on Russia than the president himself has been willing to be, at least in public. Trump in recent weeks has spoken openly about readmitting Russia into the Group of 7, the club of industrialized democracies from which it was expelled in 2014 after Putin annexed Crimea.

In the past, Trump’s informal meetings with Putin appear to have played down points of friction, particularly over the topic of Russia’s election meddling, which Putin has vehemently denied. Trump has often contended that talk of Russian election meddling is an overblown accusation meant to undercut his legitimacy, even though such statements are contrary to the findings of the U.S. intelligence community, which concluded that it was a serious effort by Putin himself.

When the two met on the sidelines of the Group of 20 summit meeting about a year ago in Hamburg, Germany, American officials said Trump confronted Putin about the election meddling, but the Russian president denied it and both agreed it was time to move beyond the matter. Russian officials said Trump had “accepted” Putin’s denial and told him that certain people in the United States were “exaggerating” the issue.