The chairman of the House Armed Services Committee on Wednesday became the highest-ranking congressional Republican to declare that the Trump administration should have implemented mandatory sanctions against Russia last month, adding to a growing bipartisan movement to put pressure on the White House to more aggressively punish the Kremlin.

Rep. Mac Thornberry (R-TX), the committee’s chairman, said he shares concerns relayed by Adm. Mike Rogers, the director of the National Security Agency and U.S. Cyber Command, who told Thornberry’s Senate counterparts on Tuesday that Russian President Vladimir Putin “has come to the conclusion that there’s little price to pay” for Moscow’s cyber-attacks aimed at disrupting elections in the United States and elsewhere.

“An aggressor will always push forward and do more until he meets resistance,” Thornberry told The Daily Beast. “There has to be a price to be paid.”

Rogers stunned lawmakers Tuesday when he said flatly that the Trump administration is not doing enough to counter what intelligence chiefs have said is an ongoing threat from the Kremlin to meddle in future American elections. He said Russia has “ not paid a price that is sufficient to change their behavior.”

Rogers was asked in particular about the administration’s decision to not immediately implement sanctions against Russia last month, under legislation that Congress passed with overwhelming majorities in both the House and Senate. Thornberry echoed Rogers’ concerns and said “of course” the administration should have implemented the sanctions. The Countering America’s Adversaries Through Sanctions Act (CAATSA) passed in the House by a margin of 419 to 3, in the Senate 98 to 2.

A State Department spokeswoman told The Daily Beast last month that officials had come to the conclusion that the sanctions regime—which consisted only of naming Russian intelligence and defense firms that would be subject to punishments—was already acting as a “deterrent” against foreign investment in those Russian entities.

The department gave lawmakers a classified briefing during which top officials outlined their case, but Democrats and a growing number of Republicans are growing increasingly dissatisfied. They’ve argued that a stronger sanctions regime is necessary in order to ensure that Russia’s covert actions during the 2016 presidential campaign won’t continue with this year’s midterm elections and those in the future.

“I think the basic premise is… they’re going to keep doing things until there’s a price to be paid,” Thornberry said. “I am very much on the side of calling them out and exposing what they’re doing.”

President Donald Trump has been reluctant to directly call out Putin, even after special counsel Robert Mueller indicted 13 Russian individuals and other entities believed to be responsible for meddling in the 2016 election. The president has referred to Mueller’s probe as a “witch hunt,” and has dismissed the Russia story as “fake news” and a “hoax.”

While Thornberry largely echoed Rogers’ criticisms, he commended the Trump administration for approving a lethal defensive weapons sale to Ukraine in December as part of its military’s ongoing battle with Kremlin-backed separatists. Moreover, even Democrats have praised the administration for moving forward with tough sanctions against Russian human-rights violators.

“I mention [Ukraine] because there’s a broad range of activities here. They’re not all online. Some of them are on the ground. And I think that’s a very positive step,” Thornberry said. “But as a country, we’re going to have to come to grips with how to deal with this attempt to manipulate us and our decisions.”

Rogers also told senators on Tuesday that he has not explicitly been granted authority from the president or other cabinet officials to wage counter-attacks against Russia’s cyber operations at their origin. Thornberry said the U.S. is “woefully behind in thinking through cyber as a domain of warfare.”

Sen. Bob Menendez (D-NJ), the ranking member of the Senate Foreign Relations Committee, sent a letter to Secretary of State Rex Tillerson on Wednesday outlining a series of concerns about the administration’s compliance with CAATSA sanctions against Russia, Iran and North Korea.

“Given what we know about Russian government interference in European elections over the last year alone, it is impossible to believe that the administration could not identify one sanctionable offense,” Menendez wrote.