Updated

Two leading U.S. senators, responding to this week’s horrific chemical attack on residents of Idlib, Syria, called Wednesday for the indictment of Syrian leader Bashar Assad for war crimes.

Sen. Marco Rubio, R-Fla., who chairs the Foreign Relations Committee’s subcommittee on human rights, and Ben Cardin, D-Md., ranking member of the Foreign Relations Committee, jointly announced they were filing legislation that would make Assad accountable for war crimes.

In addition, the two, who also co-sponsored a measure in 2014 on Syrian regimes crimes against humanity, said Russian President Vladimir Putin is an accomplice to the same war crimes.

“It was a Russian aircraft piloted by an Assad pilot,” Cardin said, adding that there is an urgent need for “a clear U.S. policy that [Assad] has no legitimacy as the leader of Syria, and no future as the leader of Syria. That should be made very clear by the pronouncements of our administration.”

Cardin said the U.N. Security Council should pass a resolution establishing a special tribunal to indict Assad and Putin.

Rubio said Putin is just as responsible for the massacre as Assad.

This latest heinous attack only strengthens our resolve to impose additional enforcement mechanisms that demonstrate the international community is serious about consequences to what amounts to yet another barbaric war crime by the Assad regime. The fact is Assad has proven once again he is a war criminal that must go.

— Sen. Robert Menendez, D-N.J., member Foreign Relations Committee

“They’re accomplices,” Rubio said. “Vladimir Putin is a war criminal who is assisting another war criminal.”

Assad’s vicious acts against his own people, Rubio said, makes Syria ripe for even more resentment and anger against its leader that can be parlayed into joining jihadist groups that are fighting him.

“They’re going to end up joining whatever organization is in Syria with the most money and the most guns to fight Assad,” Rubio said, adding that anger among people who’ve lost children to the chemical attacks would lead even those who inherently oppose jihadist groups to join them for revenge against Assad.

bb7355b4-GOP 2016 Rubio Iowa

Sen. Marco Rubio (AP)

Other options, the two senators said, are to impose additional sanctions on Russia.

Rubio said that not only is acting swiftly and firmly important for the United States’ role as a moral leader worldwide, but also for protecting national interests and global security.

Assad’s vicious acts on his own people, Rubio said, makes Syria ripe for even more resentment and anger against its leader to be parlayed into joining jihadist groups that are fighting him.

“They’re going to end up joining whatever organization is in Syria with the most money and the most guns to fight Assad,” Rubio said, adding that anger among people who’ve lost children to the chemical attacks would lead even those who inherently oppose jihadist groups to join them for revenge against Assad.

menendez and mccain

Sen. John McCain, left; Sen. Robert Menendez, right (Reuters)

Their demands for a tougher response to Assad and Putin came on the heels of similar ones made by other congressional leaders.

Other members of Congress say the chemical attack appears to be a violation of the 2013 agreement with Russia and Syria to destroy all chemical weapons in the Middle Eastern country. Witnesses of the attack said the chemical used in the bombing appears to be sarin.

Sen. Robert Menendez, D-N.J., former chair of the Foreign Relations Committee and a current member of the panel, called Assad a war criminal and said the Trump administration must take “solid action” that reaffirms our support for the Syrian people in their efforts to remove Assad from power.

"This latest heinous attack only strengthens our resolve to impose additional enforcement mechanisms that demonstrate the international community is serious about consequences to what amounts to yet another barbaric war crime by the Assad regime,” Menendez said. “The fact is Assad has proven once again he is a war criminal that must go.”

Senate Armed Services Chairman John McCain, an Arizona Republican who has pushed for a stronger approach to Syria, took aim at statements by Secretary of State Rex Tillerson and U.N. Ambassador Nikki Haley that suggested the U.S. is better off not focusing on Assad when it comes to its Syrian policy.

McCain theorized that Haley’s remarks might have given Assad the idea that he could commit a heinous act without repercussions.

He said not prioritizing taking action on Syria is "another disgraceful chapter in American history."

"(Syrian President) Bashar Assad and his friends, the Russians, take note of what Americans say," he said to CNN's Alisyn Camerota on "New Day." "I'm sure they took note of what our Secretary of State (Rex Tillerson) said just the other day that the Syrian people would be determining their own future themselves -- one of the more incredible statements I've ever heard."

At the press conference on Wednesday, Rubio agreed that Tillerson's remarks likely encouraged Assad to launch his bold assault on his own citizens.

"I don't believe that it is coincidental," Rubio said.

Rubio added that he believes Tillerson did not intend for, or foresee, his remarks to become an incentive for Assad to do what he is believed to have done. The senator said Assad has used chemicals on a smaller scale on his citizens many times before, and that he likely would aimed for a larger attack sooner or later.

Menendez also took the Kremlin to task for the horrific attack.

“While we must hold [Assad] accountable for this act which would constitute a war crime, we must also condemn Vladimir Putin and Russia, who have enabled the Assad regime to hold on to power for this long.”

While Putin must be held to account, Menendez said it was clear that ultimate responsibility for the attack was with Assad.

“An attack using aircraft to deliver these sophisticated, ruthless and banned chemical weapons could only have been ordered by Bashar Assad,” Menendez said to Fox News. “We know that this ruthless dictator has no regard for human life, and no remorse for the horrific attacks he continues to perpetrate against his own citizens.”

Some experts say that a military move to oust Assad is much more complex than many who are calling for one make it appear.

Brent Sasley, a political scientist at the University of Texas in Arlington who has authored numerous articles on the Middle East, told Fox News that direct involvement in the removal of Assad could be more detrimental for the international community than dealing with him in alternative ways.

Sasley said any military moves against Assad would, by definition, also mean direct confrontations against Iran and Russia – supporters of the Syrian regime who are entrenched in that country’s civil war.

“They’ve clearly committed themselves to the Assad regime, now they’re physically involved in Syria to the extent they weren’t before,” Sasley said, referring to the 2013 chemical attack in Syria that killed nearly 1,500 people, including more than 400 children.

“There’s no way to eject Assad without the massive use of American troops and allied troops," Sasley said. "The Trump team is in an extremely difficult position. Anything serious and substantial would entail putting us in direct confrontation with Russia, which Trump himself has tried to avoid.”