A bipartisan group of 27 U.S. senators sent a letter to President-elect Donald Trump on Thursday urging him to take a tough line against Russia over what they termed its “military land grab” in Ukraine.

The letter, whose 12 Republican and 15 Democratic signatories included some of the leading foreign policy voices in Trump’s Republican party, was an early sign that lawmakers may assert themselves on some international matters where they disagree with his White House.

Trump signaled during his campaign that he might take a softer line in dealings with Moscow, repeatedly praising Russian President Vladimir Putin’s leadership.

“In light of Russia’s continued aggression and repeated refusal to respect Ukraine’s territorial integrity and sovereign right to choose its own destiny, we also renew our call for the United States to increase political, economic and military support for Ukraine,” said the letter, led by Senators Richard Durbin, a Democrat, and Rob Portman, a Republican, who are co-chairmen of the Senate Ukraine caucus.

In the letter, which was seen by Reuters, the senators also said they believe Russia’s annexation of Crimea should not be accepted and that the United States should not lift sanctions imposed on Russia for its behavior in eastern Ukraine.

Among the Republican senators who signed the letter were John McCain, chairman of the Senate Armed Services Committee, and Lindsey Graham, head of the appropriations subcommittee that oversees the State Department.

A majority of Republicans and Democrats on the Senate Foreign Relations Committee also signed the letter.

(Reporting by Patricia Zengerle; editing by Leslie Adler)