Sens. Bob Menendez, D-N.J., and Mark Kirk, R-Ill., hope to have the bill ready for other lawmakers to consider when the Senate returns Dec. 9 from its two-week recess, according to legislative aides. Many in Congress are skeptical, if not outright hostile, to the deal reached by Iran and world powers over the weekend in Geneva.
The Kirk-Menendez measure would require the administration to certify every 30 days that Iran is adhering to the terms of the six-month interim agreement and that it hasn't been involved in any act of terrorism against the United States.
Without that certification, sanctions worth more than $1 billion a month would be re-imposed and new sanctions would be added. The new measures would include bans on investing in Iran's engineering, mining and construction industries and a global boycott of Iranian oil by 2015. Foreign companies and banks violating the sanctions would be barred from doing business in the United States.
The senators hope to send the bill to the White House before the end of the year, said the aides, who spoke on condition of anonymity because they weren't authorized to speak by name on the matter.
"I do not believe we should further reduce our sanctions, nor abstain from preparations to impose new sanctions," Menendez, the chairman of the Senate Foreign Relations Committee, said after Sunday's interim agreement was announced.
The powerful American Israel Public Affairs Committee echoed the call.
New sanctions are needed "so that Iran will face immediate consequences should it renege on its commitments or refuse to negotiate an acceptable final agreement," the group said.
Imposing stiffer economic penalties against Iran enjoys wide support in Congress. President Barack Obama has pleaded personally with lawmakers to give him more time and room for diplomatic efforts. The interim agreement promises no new penalties against Iran while it is in effect.
Administration officials say new pressure from Congress now could prompt the Iranians to walk away from the deal and cause unrest between the U.S. and its negotiating partners in the so-called P5+1 — Britain, China, France, Germany and Russia.
"We need to give diplomacy a chance to work," Tony Blinken, Obama's deputy national security adviser, said Monday on MSNBC. "New sanctions now, on top of the ones that are already in existence and will continue to be implemented, we fear would be taken as a sign of bad faith, not just by the Iranians but, indeed, by our partners in the P5+1 and other countries around the world whose co-operation we require to implement the sanctions and make them effective."
Blinken said sanctions can be turned up "on a dime" six months from now if no comprehensive agreement is reached in the interim.
Senate Majority Leader Harry Reid, D-Nev., has yet to determine how he'll react to the agreement, Democratic aides said.
Reid said last week that the Senate would move forward with new sanctions when lawmakers return from their Thanksgiving break. But he took a more cautious approach Monday, saying on NPR's "Diane Rehm Show" that Menendez and Sen. Tim Johnson, D-S.D., chairman of the Senate Banking Committee, will study the interim agreement with Iran and "hold hearings if necessary."
"If we need work on this, if we need stronger sanctions, I am sure we will do that," Reid said.
The interim agreement allows Iran to keep central elements of its nuclear program, which it says is for peaceful purposes only, while capping its uranium enrichment to levels well below the concentration of fissionable material needed for nuclear weapons. Iran also must grant U.N. inspectors greater access to nuclear sites, neutralize higher-enriched uranium stockpiles and halt work on a planned heavy water reactor near Arak.
In exchange, Iran receives about $7 billion in relief over the next six months from international sanctions that have crippled its economy. More than half of that amount comes from money now in frozen accounts to which the Iranians will be given access. Iran also will be allowed to restart limited sales of petrochemicals and other products.
Having voted new sanctions against Iran four months ago, the House is waiting for the Senate to act. The House would likely give overwhelming support to any new legislation against Iran, given that it voted 400-20 in favour of new penalties in July.
The administration wants no new sanctions laws enacted while the world tests Iran's seriousness to curb its nuclear program. That applies even if the fresh sanctions come with wide waiver authority, according to congressional aides who have spoken with administration officials.
To that end, Secretary of State John Kerry planned a series of conference and private telephone calls with key lawmakers this week.
Mark Dubowitz, an Iran sanctions expert at the Foundation for Defence of Democracies, said Obama would be wise to back a kind of sanctions-in-waiting law from Congress at this time, if only to remind countries around the world that Iran isn't open for business.
The Kirk-Menendez bill "would be a gift to Obama and would help prevent the unraveling of the sanctions regime," Dubowitz said. "The sanctions were about fear and now the market psychology is changing from fear to greed. Greed overrides fear."