Iran and six world powers have broken off weeklong negotiations in Switzerland on curbing Tehran's nuclear program and were set to reconvene next week.
An Iranian delegation has been meeting in the Swiss city of Lausanne with officials from the United States, Britain, France, Germany, China, and Russia seeking a deal to limit Tehran's nuclear program in exchange for relief from economic sanctions.
Iran says its nuclear program is purely for peaceful purposes.
A framework agreement is due by March 31 and a full deal by June 30.
It was reported on March 20 that the Iranian delegation at the nuclear talks in Lausanne was returning to Tehran for the funeral of President Hassan Rohani's mother or to mark Norouz, the Persian New Year.
Rohani's mother, who was 90 years old, reportedly died earlier in the day.
The United States announced that Secretary of State John Kerry is to travel to London on March 21 to meet with his British, French, and German counterparts to discuss progress in negotiations with Iran.
State Department spokesman Jeff Rathke said Kerry had already spoken to officials from China and Russia about the ongoing talks.
The secretary of state said "a lot of progress" has been made during the nuclear talks with Iran, adding that they would resume next week in Lausanne.
Iranian Deputy Foreign Minister Abbas Araqchi said talks would resume on March 25.
Iranian Foreign Minister Mohammad Javad Zarif said that there was "no reason" to report an agreement is at hand.
In a video message for Norouz, U.S. President Barack Obama told the Iranian people that a deal to transform the relationship between the two countries could be within reach, but conceded there were still "gaps" in negotiations.
"This year, we have the best opportunity in decades to pursue a different future between our countries," the president said.
In an apparent response to Obama's video message, Zarif said, "Iranians have already made their choice: Engage with dignity.”
“It's high time for the U.S. and its allies to choose: pressure or agreement," he wrote on Twitter.
On March 20, Obama discussed the nuclear talks with Iran in a phone call with French President Francois Hollande, the White House said in a statement.
“The presidents reaffirmed their commitment to achieving a long term comprehensive deal that fully and verifiably addresses the international community’s concerns about Iran’s nuclear program, while noting that Iran must take steps to resolve several remaining issues,” the statement said.
The call came amid reports of disagreement between the U.S. and France over the issue of easing of sanctions.
The Guardian reported that the U.S has proposed a gradual lifting of sanctions in return for concrete actions by Iran to limit its nuclear program. Meanwhile, France wants only “a symbolic easing” of the sanctions imposed over the last decade, the British daily reported.
European diplomats told The Wall Street Journal that France fears the quick repeal of the penalties could lead to the collapse of the West’s financial leverage over Tehran.