The Council of the European Union issued a statement in support of the engagement strategy with Iran, while at the same time expressing concern over Iran's nuclear intentions.
"Iran must restore confidence in an exclusively peaceful nature of its nuclear activities," the statement said.
Iran maintains its controversial nuclear program is for civilian energy purposes, though international regulators reported Tehran's nuclear ambitions are ambiguous despite years of monitoring.
The EU called on Tehran to take advantage of the Washington position, saying, "The evolution of our relations with Iran will also depend on it."
Meanwhile, a bipartisan effort by 25 U.S. senators, led by Evan Bayh, D-Ind., Joe Lieberman, I-Conn., and Jon Kyl, R-Ariz., introduced the Iran Refined Petroleum Sanctions Act to supplement existing legislation penalizing trade in the Iranian energy sector.
Calling the oil and gas industry in Iran the "Achilles' heel" of the clerical leaders, the new legislation authorizes harsh penalties on shipping, insurance and financial entities selling gasoline or refined petroleum products to Iran, including a ban on activity in the United States.
"By empowering the president in this way, we make it more likely engagement with the Iranians will succeed, and they will peacefully abandon their nuclear ambitions," Bayh said.
Obama extended the punitive Iran Sanctions Act of 1996 for another year on March 13.