U.S. Secretary of State John Kerry said on Thursday he may meet Iran's foreign minister again this week to discuss Tehran's nuclear program following their roughly six hours of talks on Wednesday.
Iran and six world powers have renewed their quest for an elusive nuclear deal - seen as crucial to reducing the risk of a wider Middle East war - after negotiators failed for the second time in November to meet a self-imposed deadline.
The major powers hope to persuade Iran to curb its nuclear program, which the West suspects may seek to develop atomic weapons, in exchange for a gradual easing of economic sanctions. Iran says its nuclear program is solely for peaceful purposes.
Kerry and Iranian Foreign Minister Mohammad Javad Zarif met for about six hours in Geneva on Wednesday.
"There is no final decision as to whether or not we will meet in Paris," Kerry told reporters in the Bulgarian capital Sofia, noting he and Zarif would both be in the French capital on Friday.
"It is possible, but nothing has been decided. It may also not happen," he added.
Kerry sidestepped a question on whether it was possible for the United States to strike a nuclear deal while Iran continues to detain a number of U.S. citizens, saying only that Washington was making great efforts to secure their release.
Zarif met with European Union foreign policy chief Federica Mogherini in Brussels on Thursday. The EU said in a statement that they both agreed that time cannot be wasted in trying to secure an agreement.
"We affirmed our strong commitment to a diplomatic solution which would fully address international concerns about the exclusively peaceful nature of the Iranian nuclear issue," said Mogherini. "Negotiations have to be brought to a conclusion in line with the agreed time."
The new deadline for a long-term nuclear agreement between Iran and the six powers - the United States, Britain, France, Germany, Russia and China - is June 30.
Mogherini's predecessor Catherine Ashton is the EU envoy to the nuclear talks. The EU has been coordinating the meetings between Iran and the six powers. Senior foreign ministry officials from Iran and the powers resume talks on Jan. 18.