Catherine Ashton & Hillary Clinton

The United States and the European Union have welcomed Iran’s letter that shows a willingness to resume talks on the country’s nuclear program.

In a joint news conference on Friday morning, U.S. Secretary of State Hillary Clinton and EU foreign affairs chief Catherine Ashton expressed optimism about the new development, saying: “We think this is an important step and we welcome the letter.”

They added, however, that the resumed talks “will have to be a sustained effort that can produce results.”

Saeed Jalili, the head of Iran’s National Security Supreme Council, sent a letter to Ashton to express Iran’s willingness to resume nuclear negotiations with the G5+1.

In the letter, Jalili writes: “We are ready to discuss a range of different issues that could pave the way toward constructive and long-term cooperation.”

It adds: “A constructive and positive approach to the new Islamic Republic initiatives in this round of negotiations can create a positive outlook for our talks.”

Iran’s letter was in response to a letter that Ashton sent last September, urging Iran to return to the table for “constructive” talks.

The U.S. and EU’s newfound optimism follows their imposition of harsh unilateral sanctions against Iran’s financial and energy sectors. That appears to have affected the Islamic Republic economy by destabilizing the currency market.