With National Security Adviser John Bolton threatening to "come after" Iran this week and President Donald Trump accusing the country of sowing "chaos, death, and destruction," Sen. Tom Udall (D-N.M.) was joined Wednesday by several other members of the Democratic caucus in urging Congress to ensure that the U.S. avoids yet another prolonged war by passing legislation affirming that a preemptive attack on the country would be illegal.

The Prevention of Unconstitutional War with Iran Act of 2018 demands that the president obtain congressional approval for any military action in Iran. Sens. Patrick Leahy (D-Vt.), Dianne Feinstein (D-Calif.), Richard Durbin (D-Ill.), Bernie Sanders (I-Vt.), Jeff Merkley (D-Ore.), Martin Heinrich (D-N.M.), and Chris Murphy (D-Conn.) signed on as co-sponsors.

"Every day, the president and his saber-rattling foreign policy advisers like John Bolton are inching us closer and closer to conflict, endangering our national security, jeopardizing our diplomatic interests and alarming our allies." —Sen. Tom Udall (D-N.M.)

"The administration's approach to Iran is ripped straight out of the same playbook that launched us into the failed invasion of Iraq, and Congress needs to assert its constitutional authority and halt the march to war," said Udall. "Every day, the president and his saber-rattling foreign policy advisors like John Bolton are inching us closer and closer to conflict, endangering our national security, jeopardizing our diplomatic interests and alarming our allies. The consequences of war with Iran would be catastrophic, risking the lives of thousands of Americans while squandering our global reputation, with little chance of improving our long-term security."

The bill was introduced a day after Bolton told a gathering of anti-Iran activists that there would be "hell to pay" if Tehran "crossed" the U.S. or its allies.

Anti-war advocates praised Udall's proposal, especially in light of the president's numerous aggressive military actions in foreign countries since he entered office less than two years ago.

"The Constitution clearly states that Congress, not the president, is the arbiter of when we go to war," said Paul Kawika Martin of Peace Action. "The Trump administration has repeatedly overstepped its war powers in Syria and Yemen, and seems eager to provoke a war with Iran. Senator Udall's legislation is a timely reminder that Trump has no authority to go to war with Iran without congressional authorization. Voters overwhelmingly think the Iraq War was a mistake; a war with Iran would be exponentially worse."

After nearly 30 people were killed in a terrorist attack at a parade in Iran over the weekend, President Hassan Rouhani and other observers suggested that a U.S.-backed Gulf State—possibly Saudi Arabia or the United Arab Emirates (UAE)—was to blame. The attack came amid rising tension between the U.S. and Iran after Trump pulled out of the 2015 nuclear deal that the Obama administration and five other countries had reached with Tehran, and reimposed punishing sanctions on the country.

Rouhani opened the door to a meeting with Trump at the U.N. General Assembly this week, but the president refused.

"The Constitution is very clear: it is the Congress, not the president, that has the authority to decide when our country goes to war," said Sanders. "Since taking office, the Trump administration has pursued an extremely hostile and provocative policy against Iran. This bill makes clear that the Trump administration does not have authority to use the military for that purpose. We should be pursuing diplomacy to get Iran to change its problematic behavior, not war."