Senate Democrats have some friendly suggestions for topics that President Donald Trump should discuss with Russian President Vladimir Putin during their meeting in Germany, scheduled for Friday.

In a letter sent to Trump just as he landed in Hamburg, Germany, on Thursday, five senior Democrats make the case that Russia’s meddling in the 2016 presidential election should be at the top of the agenda.

“Put more simply, President Putin directed an attack on the most central tenet of our democracy — our election. Not raising this matter with President Putin would be a severe dereliction of the duty of the office to which you were elected,” the senators wrote.

Senate Minority Leader Charles E. Schumer of New York led the letter, joined by Minority Whip Richard J. Durbin of Illinois, Armed Services ranking member Jack Reed of Rhode Island, Foreign Relations ranking member Benjamin L. Cardin of Maryland and Intelligence Vice Chairman Mark Warner of Virginia.

The Democrats said they expected a Senate-passed bill imposing additional sanctions on Russia to clear through Congress “in short order.” They want Trump to warn Putin against any attempts to interfere in either the 2017 or 2018 elections in the United States.

Several states, including Warner’s home state of Virginia, as well as New Jersey, have significant off-year elections, and, of course, 2018 will bring a new round of midterm elections.

“No candidate, Democrat, Republican or independent, wants to have President Putin and his cronies manipulating his or her electorate. And, it’s critical that both the Executive and Legislative branches of our government use every tool at our disposal to ensure that Putin does not believe he has a freehand to implement his manipulative program of election interference ever again,” the senators wrote. “The upcoming elections cannot be a playground for President Putin.”

In Poland, Trump on Thursday called for Russia “to cease its destabilizing activities in Ukraine and elsewhere.”

When asked about the Russian efforts to interfere in the 2016 campaign, however, Trump told reporters that “nobody really knows for sure.”

“I think it could very well have been Russia. I think it could well have been other countries. I won’t be specific,” Trump said during a news conference.