House Republicans on Thursday stopped Democrats from advancing a measure aimed at ending U.S. military operations against Iran, continuing to resist efforts to place limits on President Donald Trump’s war powers.

Rep. Chris Smith of New Jersey presided over a brief “pro forma” session and adjourned it before Democrats were able to attempt passage of the resolution through unanimous consent.

In recent months, Democrats in both chambers of Congress have repeatedly tried—and failed—to pass war powers resolutions that would require Trump to obtain legislative approval before initiating military action, including in situations involving Venezuela and Iran.

Concern among Democrats intensified after Trump warned earlier in the week that “a whole civilization will die,” prompting dozens of lawmakers to call for his removal from office. The 1949 Geneva Conventions on humanitarian conduct in war prohibit attacks on sites considered essential for civilians.

“Threatening genocide is not a negotiating tactic,” Rep. Sara Jacobs, D-Calif., said at a press conference outside the Capitol following the pro forma session, which was held while Congress is out of Washington during a two-week Easter recess.

Trump announced Tuesday that he had agreed to a ceasefire in the U.S.-Israel conflict with Iran, doing so less than two hours before a deadline he had set for Tehran to reopen the Strait of Hormuz or face severe strikes on its civilian infrastructure.

The White House has defended Trump’s actions, saying they are lawful and fall within his authority as commander-in-chief to order limited military operations to protect the United States.

Iran has maintained that its nuclear program is peaceful. The Trump administration has described the conflict as a decisive success, even as the top U.S. military officer said American forces remain ready to resume fighting if needed.

Republicans, who hold narrow majorities in both the House and Senate, have largely united behind Trump and backed his policies.

While the U.S. Constitution gives Congress the authority to declare war, that requirement does not apply to short-term military actions or situations involving an immediate threat to the country.