There was a bipartisan delegation of US politicians to the Finnish president Sauli Niinistö, a little over a week in advance to Trump's visit.
https://twitter.com/jeffflake/status/1015002454382047232?s=21
Niinistö's PR person says that the meeting was scheduled before it was known that Trump and Putin would be meeting, but I think what happened is worth a mention anyway. In any case, both the upcoming NATO summit and the Trump/Putin meeting were discussed. I know that Jeff Flake at least is known for being opposed to Trump, and Ed Royce is not running for re-election, and that's just from what was barely more than a cursory glance. Niinistö in turn is a pro-EU globalist who was the Finance Minister during the successful push to make Finland join the EU. Right after the EU vote had come up "yes", it turned out that we had supposedly voted to give up the Finnish mark too. Strange how we weren't told about that ahead of the time. The knowledge could have flipped the vote. I was there and I remember it. Niinistö as the Finance Minister was an integral part of making Finland give up its own money with just a unilateral announcement from the government.
Articles in Finnish:
https://www.is.fi/kotimaa/art-2000005747593.html
https://www.iltalehti.fi/politiikka/201807052201056235_pi.shtml
The delegation:
Senator Jeff Flake (R)
Senator Bob Corker (R)
Senator Chris Coons (D)
Senator Tom Udall (D)
Congressman Ed Royce (R)