Jon Huntsman, the U.S. ambassador to Russia, warned in a closed-door briefing with lawmakers on Tuesday that the U.S.-Russia relationship would be “done” if the Kremlin tries to interfere in the 2018 midterm elections.

A source who attended the briefing, which took place with members of the House Foreign Affairs Committee, told The Daily Beast that Huntsman was unequivocal in stating that Russia interfered in the 2016 election. He said that as a former governor of Utah, he is deeply concerned about the idea of the Kremlin attempting to interfere with election rolls in individual states and localities. And he offered a stark warning: Russian actors were on course to meddle in U.S. elections again in 2018 and 2020, in addition to elections in other countries.

“I don’t think Russia is going to quit,” Huntsman told the nine Republican and 12 Democratic members who attended the briefing, according to the source who spoke on the condition of anonymity. “Putin probably has never been stronger.”

The briefing, which lasted an hour, marked a stark contrast in tone from President Donald Trump himself, who has been notably deferential toward Russia and often unwilling to acknowledge its history of election interference. Huntsman’s remarks fit into a pattern whereby top administration officials—even cabinet secretaries—are more willing than the president to embrace tougher rhetoric on policies when it comes to Russia.

Rep. David Cicilline (D-R.I.) asked Huntsman about those equivocations from Trump during the meeting, the source said. But Huntsman did not comment. Huntsman did, however, tell lawmakers that he brings up election interference in all of his meetings with Russian officials, and that those officials denied that they were behind any electoral interference in 2016.

The briefing also provided lawmakers with a rare opportunity to meet with Huntsman, who impressed members from both sides of the aisle with his firm statements about Russia’s intentions to throw democracies around the world into chaos.

In addition to discussing past and future electoral interference, Huntsman also addressed the rollout of new sanctions against Russia, which Democratic and Republican lawmakers argue has been insufficient and delayed. During the briefing, the ambassador pledged that the Trump administration will meet the Jan. 29 deadline for implementing sanctions against individuals and entities that are doing business with the Russian intelligence and defense sectors.

Lawmakers on both sides of the aisle have accused the administration of stonewalling on the sanctions, which Trump reluctantly signed into law last year after the legislation passed with overwhelming majorities in both the House and Senate. The administration had tried—but failed—to water down the sanctions, and top officials were dispatched to Capitol Hill last year in an effort to convince lawmakers to drop a key provision that the White House believes handicaps Trump’s authority to unilaterally lift or ramp up sanctions.

Lawmakers did not question Huntsman specifically about the administration’s delay in implementing and rolling out those sanctions, the source said. Huntsman added that he expects that the new round of sanctions will cause ripples in the U.S. relationship with Russia. He also questioned whether the U.S. will reach a “point of diminishing returns” in altering Russia’s geopolitical behavior by implementing even more sanctions, arguing that such measures “cease to be a tool” if nobody cares about them. The source interpreted that as a potential preview of a shift in U.S. policy.

“Massive bipartisan majorities passed sanctions on Russia for election interference because everyone knows Russia did it,” the source said. “Ambassador Huntsman’s a smart, seasoned diplomat. He's not going to tell lawmakers that up is down, even if we continue to hear bizarre denials from elsewhere in the administration.”

Later Tuesday morning, Huntsman was spotted at the White House. It is unclear whether Trump met with Huntsman, but a meeting was not on Trump’s daily schedule.