The 99-to-0 vote Thursday showed the desire of lawmakers to maintain a tough posture toward Iran amid uncertainty over the future of the nuclear agreement, which President-elect Donald J. Trump railed against during his campaign.

“Given Iran’s continued pattern of aggression and the country’s persistent efforts to expand its sphere of influence across the region, preserving these sanctions is critical,” the Senate majority leader, Mitch McConnell of Kentucky, said on Thursday. He said he expected the Trump administration and the new Congress to “undertake a total review of our overall Iran policy.”

Asked on Wednesday if the president would veto the extension of sanctions, the White House press secretary, Josh Earnest, said that the administration would review it. “The administration continues to retain substantial authorities that can be used to impose financial sanctions on the Iranian regime,” he said.