WASHINGTON (NEXSTAR) — Members of the newly formed “No War with Iran” Caucus say they want President Donald Trump to understand that he must have congressional authorization for any use of force against Iran.

House Democrats are urging the president to take a much more diplomatic approach to the escalating conflict.

“This is amateur hour in the White House,” said Congressman Peter Welch, D-Vermont.

“We are afraid that this president is going to bumble and fumble his way into war,” added Congressman Jim McGovern, D-Massachusetts.

The caucus hopes their collective votes can serve as a check and balance to Trump and emphasize that the president must go through Congress for authorization of any use of force.

“This is a crisis of the president’s own making,” McGovern added.

In a tweet on Tuesday, Trump said: “any attack by Iran on anything American will be met with great and overwhelming force.”

McGovern says Trump’s approach to the situation has been inconsistent.

“I have whiplash just trying to follow him from hour to hour, from day to day,” he said. “One day he rattles the sabers, talks about going to war, and then at the last minute, he says we’re not going to war.”

Welch says every step the president takes narrows the options available to maintain peace.

“If he’s going to be for peace – act like it,” Welch said. “You can’t have it both ways, Mr. President.”

Some Republicans say they trust Trump and believe his approach will pay off.

“The president has put them on warning. He put them on warning that he can make additional military steps if necessary, but right now he’s doing the prudent response,” said Congressman John Joyce, R-Pennsylvania.

Despite that support from some Republicans, Democrats will now move an amendment to the Defense Authorization bill that blocks a strike against Iran without congressional approval.