The alleged Iranian government-backed plot to assassinate the Saudi ambassador to the United States is quickly exacerbating already flaring tensions between Washington and Tehran.

Members of Congress were quick to condemn Iran over the plot.

Rep. Michael McCaul R-Texas, said if it was indeed sponsored by the Iranian government, "this would constitute an act of war not only against the Saudis and Israelis but against the United States as well."

Rep. Peter King, R-N.Y., issued a similar statement saying, "Iran's assassination of a foreign diplomat in our country would have violated both U.S. and international law, and represented an act of war."

Rep. Ted Poe, R-Texas, speaking on Fox News, called the plot an "act of war" against the United States.

"We have to do something," he said, saying the specifics of the response should be left up to the Defense Department and the president.

But a senior Defense official told Fox News the announcement Tuesday "is not a trip wire for military action in Iran."

"No one should read into this as a pretense for any type of military response," another senior Defense official added.

Speaking to Fox News on the condition of anonymity due to the sensitive nature of the subject, the officials said the Pentagon sees the alleged plot as a criminal act that is rightly being handled by the Department of Justice.

Late Tuesday night, the State Department issued a travel alert for Americans, warning those at home and aboard to watch out for possible attacks linked to the alleged plot.

Attorney General Eric Holder, in announcing the plot and criminal charges filed against two individuals, would not say exactly how high up the plot went in the Iranian government. He said it was "directed and approved by elements of the Iranian government," specifically noting the alleged involvement of members of Iran's special operations Quds Force.

But U.S. officials made clear they will use the plot to marshal international pressure against the regime.

"The United States is committed to holding Iran accountable for its actions," Holder said.

A State Department official on Tuesday called the case a "flagrant violation of international law."

And Secretary of State Hillary Clinton said the U.S. would work with its allies to "send a very strong message that this kind of action, which violates international norms, must be ended."

In a separate interview with the Associated Press, Clinton said the plot "crosses a line," and that she and President Obama were calling international leaders to tell them what happened. She said they want to "pre-empt" any efforts by Iran to deny responsibility, as well as "enlist more countries in working together against what is becoming a clearer and clearer threat" from Iran, according to the Associated Press. She said the reaction could "further isolate Iran."

The Treasury Department fired the first diplomatic shot Tuesday afternoon, imposing sanctions on five people allegedly linked to the plot, including four members of the Quds Force -- which is part of the Islamic Revolutionary Guard Corps. Two of them, Manssor Arbabsiar and Gholam Shakuri, were charged Tuesday in New York federal court, though Skahuri remains at large. The Treasury Department said the other Quds officials named were also involved in the plot. The sanctions will freeze any U.S. assets held by the individuals and prohibit anyone in the U.S. from doing business with them.

U.S. officials say the suspects in the case were working on a "murder for hire" scheme to kill the Saudi ambassador to the United States using explosives. They allegedly reached out to a U.S. source in Mexico posing as a drug cartel representative. Arbabsiar allegedly tried to hire the source and his accomplices to carry out the attack.

Arbabsiar, who was arrested by federal agents on Sept. 29, later confessed to his involvement and said senior Quds officials were directing the plot, according to the Justice Department.

A brief analysis from Stratfor Global Intelligence cautioned against any claims of high-up Iranian involvement. The analysis said the plot as described "seems far-fetched" considering "its ramifications would involve substantial political risk."

"Iran has been known to carry out preoperational surveillance in the United States, but it has not yet used this intelligence to carry out a high-profile attack," the analysis said, suggesting the Tehran links were "exaggerated."

An Iranian representative at the United Nations has denied the U.S. allegations.

But Clinton said in the AP interview Tuesday that the claims are "well-founded."

Clinton plans to meet Wednesday with the Swiss ambassador to Iran, a meeting that will surely provide an opportunity to address the allegations unveiled Tuesday. The Swiss serve as the United States' diplomatic representatives in Iran in the absence of any formal U.S.-Iran relations.