"Now is the time to ratchet up the pressure," Rep. Ted Deutch (D., Fla.) said in an interview this week.
Rep. Ileana Ros-Lehtinen (R., Fla.), chairwoman of the House Foreign Affairs Committee, and Sen. Tim Johnson (D., S.D.), chairman of the Senate Banking Committee, have been negotiating behind closed doors for several weeks to reach consensus on sanctions legislation that the House passed in December and the Senate approved in May.
About a half dozen Republicans and Democrats who favor fierce penalties are determined to see the toughest measure yet and have been insisting to negotiators that a watered-down bill is unacceptable.
"We owe it to the American people to exhaust every possible non-military option to prevent Iran from acquiring a nuclear weapons capability," Sen. Mark Kirk (R., Ill.) said in a statement.
Rep. Robert Dold (R., Ill.) and Rep. Brad Sherman (D., Calif.) sent a letter this week to the negotiators calling for a final bill that includes a provision declaring Iran's energy sector "a zone of proliferation concern." The blacklisting would bar all transactions with the state-run National Iranian Oil Co. "This would have the effect of making virtually any transaction with - and provision of services for - the firms in Iran's energy sector sanctionable," Dold and Sherman wrote.
The lawmakers also said any legislation should include sanctions on insurance companies that knowingly provide coverage to an entity that has already been penalized. They also are pressing for sanctions on the directors and shareholders of organizations such as SWIFT, the Society for Worldwide Interbank Financial Telecommunications, unless they stop providing services to the Central Bank of Iran.
"If diplomacy is to succeed in ending Iran's nuclear weapons program, we must enact tough legislation now," the two wrote. "Sanctions are having a real impact on Iran's economy, but not yet enough to change the regime's strategic calculus."
The bill the House passed last year would restrict foreign subsidiaries of U.S. companies from doing business with Iran. The Senate-passed bill would require companies that trade on the U.S. stock exchange to disclose Iran-related business to the Securities and Exchange Commission, and expand penalties for energy and uranium mining ventures with Tehran.