The Congress is weighing a number of additional sanctions on Iran, legislation that has taken on a higher profile because of concerns about Tehran's nuclear program.
Some of the measures advanced late last year. Sanctions on foreign banks handling transactions related to Iranian oil sales became law on December 31.
The administration of President Barack Obama is now determining how aggressively it will implement those sanctions, and could begin applying them in late June.
The House of Representatives passed legislation on December 14 that would expand oil-related sanctions on Iran and close other loopholes.
Some of those additional measures are included in a Senate bill that was first introduced in May 2011.
Senators will take another look at Iran sanctions when they return to Washington later this month.
"I think the likelihood of further meaningful sanctions and further symbolic sanctions are both high," said Jon Alterman, director and senior fellow with the Center for Strategic and International Studies' Middle East program.
"What mix and when is going to depend partly on Iranian behavior and partly on American domestic politics and partly on projected impacts on global trade," Alterman said.
The U.S. government may want to analyze whether its new sanctions have the impact of encouraging Iranian cooperation before applying more sanctions, Alterman noted.
The oil-related measures under consideration include:
- Banning ships from U.S. ports that have recently landed in Iran, North Korea or Syria. The House-passed legislation would ban ships that have visited the ports within the previous two years. The Senate bill would deny entry to ships that had been to the countries in the previous 180 days.
- Sanctions on affiliates of Iran's Revolutionary Guard Corps, including any foreign entities conducting energy business with Iran, and any entities that refine, ship, broker, finance, underwrite or insure oil or natural gas.
- Sanctioning companies providing a wide range of support to help build, maintain, repair or expand Iran's ability to refine, transport or ship oil.
- Sanctioning companies involved in joint ventures with Iran involving oil development outside of the country.
- New detailed reports on foreign investors in Iran's energy sector, exporters of gasoline to Iran and buyers of Iranian oil and gas.
- Also at the committee stage in both the House and Senate are bills that would sanction classification societies that inspect and certify ships for Iran, North Korea, Sudan or Syria.
(Reporting by Susan Cornwell, Timothy Gardner and Roberta Rampton; editing by Todd Eastham)