Censor.NET reports referring to Portman's website.
Trump is encouraged to prioritize U.S. relationship with longstanding allies and increase support for institutions and European governments that help preserve the international order.
"We strongly encourage you to meet with senior leaders from Ukraine, including President Petro Poroshenko, in advance of any official meetings with senior Russian officials including Russian President Vladimir Putin," the letter says.
"Meeting with democratically elected representatives from Ukraine would send a strong signal that the United States continues to prioritize our relationship with longstanding allies, and will continue our commitments to support Ukraine's sovereignty and territorial integrity in the face of ongoing aggression," the senators add.
Portman was joined in sending the letter by Senators Bob Menendez (D-NJ), John McCain (R-AZ), Bob Casey (D-PA), James Inhofe (R-OK), and Jeanne Shaheen (D-NH).
Related materials: President Trump
US reassured Ukraine FM Klimkin of maintaining sanctions against Russia until Crimea return, Minsk implementation, - Foreign Ministry(0)