Republican senators who recently returned from Moscow have some advice for President Donald Trump ahead of his meeting Monday in Helsinki with Russian President Vladimir Putin: Be prepared, be careful and try not to be alone.

“He better know the right Russian psyche,” said Senate Appropriations Chairman Richard C. Shelby. “All he’s got to do is start with Stalin and come on up and see what’s changed.”

The Alabama Republican led the delegation, which met with senior Russian officials, including Foreign Minister Sergey Lavrov.

Sen. Jerry Moran of Kansas, who was on the trip, said in an interview that he had particular concerns about the possibility of Russian media entities misreporting the outcome of any one-on-one meeting between Trump and Putin.

“They’re propagandists. When I read what the Russian press said that transpired in those meetings, I don’t know why — I don’t believe them when they say they weren’t involved in meddling in U.S. elections,” Moran said. “I don’t know why people would believe them when they say their description of the meeting.”

“There is value in protecting the president in having a number of Americans in the room when the conversations take place, because just what I saw on the scale of a congressional visit can happen in a presidential visit in which the description of what transpired in the meeting does not fit reality,” Moran said.

Watch: McConnell Says ‘Nothing Wrong’ With Trump, Putin Meeting

Senate Republican Conference Chairman John Thune, who also traveled to Russia, said Trump should be prepared for complete denials and well-rehearsed answers when he meets with Putin in Finland’s capital.

“I think he has to expect they’re going to deny, deny everything,” the South Dakotan said. “I would think that Putin would be very well prepared, obviously, with answers … that they’ve been thinking about for a long time.”

Shelby pointed to the importance of Trump being properly briefed ahead of the sit-downs.

“It’s got to be more than a photo op. They’ve got to want to do better with us,” Shelby said. “I would imagine that President Trump will be well prepared by the National Security Council and all of his people, knowing that dealing with Putin, who will be ultra-prepared, tough, ruthless … not want to give nothing.”

Montana GOP Sen. Steve Daines suggested that Jon Huntsman, the U.S. ambassador to Russia, should be highly involved in the discussions.

“Amb. Huntsman is a tremendous asset. He is a great diplomat and a great representative for us having been ambassador to … China, Singapore and now Russia,” he said.

Dueling trips

A pair of GOP senators who have been more critical of Trump’s foreign policy took a separate trip to Europe over the July Fourth recess.

And they were more direct in expressing concerns about his treatment of allies and what he might agree to with his Russian counterpart.

Sen. Jeff Flake of Arizona wants Trump to tell Putin his invasion and occupation of the Crimea region of Ukraine is “illegal” and his activities in Syria are “detrimental.” He described U.S. allies in the region as “afraid about what our president might agree to,” and he told reporters he “very much” shares their worries.

“I just came from the region and people are genuinely concerned about how reliable we are as a partner,” said retiring Foreign Relations Chairman Bob Corker of Tennessee. “And when you have that occurring, especially with Russia’s activities, yeah, it undermines our alliance.”

NATO appetizer

The first full day of his European tour, at the NATO summit in Brussels, illustrated Trump’s complicated relationship with the leaders of other member countries.

He and first lady Melania Trump were caught on camera chatting with NATO Secretary-General Jens Stoltenberg and German Chancellor Angela Merkel during an evening reception before a working dinner. Canadian Prime Minister Justin Trudeau, full champagne flute in hand, came over to greet the first lady, and the two talked for several minutes.

Earlier in the day, Trump was on the attack, going after America’s allies even as he refused the day before to call Putin an adversary of the United States.

Trump took his war of words with America’s allies to a new level Wednesday, telling NATO’s top official that Germany is “captive” to Russia due to a recent energy deal. And he called alliance members “delinquent” on their contributions to NATO’s budget.

On both matters, Republican senators said they agreed with Trump’s message. Some were less enthused by how he delivered it, however.

“The president has a very legitimate point in that the Russians are doing some very bad things and NATO is supposed to be countering that,” said Sen. Jim Risch of Idaho, the expected next chairman of the Foreign Relations Committee if Republicans hold control of the Senate.

“Well, what you have is, you have the Germans holding hands under the table with them while we’re supposed to be disciplining them and trying to get a handle on it,” he said.

Oklahoma Sen. James M. Inhofe, who has been performing the duties of Armed Services chairman with Sen. John McCain at home in Arizona, agreed.

“People are saying, ‘He’s picking on Germany.’ Well, he was,” Inhofe said with a chuckle, criticizing the German government for “not even trying to” meet a pledge to devote more to NATO’s coffers.

“And on top of that, they’re showing in the future they’ll be even closer to Russia because of the pipeline they’re putting in,” he added. “So I think [Trump] has every justification for saying it.”

Inhofe, however, opted against giving the president any advice for his Monday summit with Putin. “You know, he’s done so well in his negotiations,” he said, “I’m not about to second-guess how he’s doing it.”

Watch: McConnell Says ‘Nothing Wrong’ With Trump, Putin Meeting