By Emily Cadei and Tim Starks, CQ Staff

News of an alleged Iranian plot to assassinate the Saudi Arabian ambassador to the United States is set to strengthen the hands of congressional hard-liners on Iran, who were already gearing up for a push to toughen sanctions this fall.

One of the first lawmakers to issue a response to the Justice Department’s disclosure Tuesday afternoon of the foiled plot was Sen. Kirsten Gillibrand, D-N.Y., a lead sponsor of legislation to increase the sanctions targeting Iran’s economy as well as human rights abuses.

“Iran has shown the world once again it poses an existential threat to the world community,” Gillibrand said in a written statement. “We must stand together and make it crystal clear — we cannot, and will not, tolerate a nuclear Iran that would pose an even greater threat. Congress must pass the Iran, North Korea and Syria Sanctions Consolidation Act, my bipartisan legislation that increases economic pressure on Iran.”

That bill (S 1048) has 72 cosponsors but has not yet been marked up in the Senate Foreign Relations Committee.

Sean O’Black, the spokesman for the Senate Banking Committee, which often shares jurisdiction of international sanctions bills, issued a statement Tuesday saying the plot “underscores the need for further tough action against Iran.”

The committee, O’Black continued, “will seek additional input from senior administration officials on how most effectively to increase pressure on Iran” at a hearing scheduled for Thursday.

The Obama administration has made clear it would prefer to focus on enforcing existing bilateral sanctions and rallying support for additional multilateral efforts to pressure Tehran.

But the new revelations of Iranian terrorism plans, as well as new reports from the United Nation’s nuclear watchdog on the country’s accelerating nuclear program, are likely to ramp up the pressure on the White House to further harden its stance. And the developments create a big opening for those lawmakers who have been agitating for another round of punitive action since the start of the year.

Already, the administration has responded with Treasury Department sanctions against five Iranians its says are associated with the assassination plot. And Secretary of State Hillary Rodham Clinton said other countries need to take new steps against Iran.

“We will be consulting with our friends and partners around the world about how we can send a very strong message that this kind of action, which violates international norms, must be ended,” she said. “And other areas where we can cooperate more closely in order to send a strong message to Iran and further isolate it from the international community will also be considered.”

Two Indicted

Authorities arrested Manssor Arbabsiar, a 56-year-old naturalized U.S. citizen holding both Iranian and U.S. passports, on Sept. 29, and filed charges against a member of the Iranian regime’s Quds security force, Gholam Shakuri, who remains at large.

According to the Justice Department, a confidential source discussed with Arbabsiar the possibility of bombing a restaurant where the Saudi ambassador was dining, and when the source “noted that others could be killed in the attack, including U.S. senators who dine at the restaurant, Arbabsiar allegedly dismissed these concerns as ‘no big deal.’ ”