Democratic Sen. Tom Udall, N.M., an opponent of President Obama’s call for military strikes on Syria, said Sunday he feared the nation was moving too quickly toward an “act of war” and had not exhausted all diplomatic efforts.

Udall voted against a measure advanced in the Senate Foreign Relations Committee last week to authorize a U.S. military attack and said he stood by that vote.

“I haven’t changed my mind,” said Udall on NBC’s “Meet the Press,” arguing that Obama had failed to make a strong case for intervention.

Udall called a chemical attack by Assad’s forces on civilians “a heinous act” and “despicable” but warned that the American public did not want to be “embroiled in a middle Eastern civil war.”

“This is an act of war we are going to take,” he added. “We haven’t exhausted all of our political, economic and diplomatic alternatives and that’s where I want to be focusing. We ought to be rallying the world.”

Udall said he was “very disappointed” that the administration “had given up.”

“They have given up on the United Nations and on rallying the world.”

The full Senate could vote on the Syria authorization as early as this week.