Washington: In a sign that keenly watched Iran nuclear talks will go down to the wire, top US diplomat John Kerry has cancelled plans to attend a key event in Boston on Monday to remain at the negotiations in Switzerland.
"Secretary Kerry was very much looking forward to being a part of the Edward M. Kennedy Institute`s dedication in Boston this week," deputy State Department spokeswoman Marie Harf said Sunday.
"Given the ongoing nuclear negotiations in Switzerland, the secretary regrets he will not be able to share this special time ... in person."
Global powers are gathered in the Swiss town of Lausanne seeking to pin down the broad outlines of a deal to rein in Iran`s suspect nuclear programme by a Tuesday deadline.
President Barack Obama is to attend Monday`s dedication of the new institute in the memory of late Massachusetts senator Ted Kennedy, who became a long-time friend of Kerry when they worked together to represent the state in the US Senate.
Organisers had announced that Kerry would join Obama, First Lady Michelle Obama and Vice President Joe Biden and deliver remarks at Monday`s ceremony.
But Kerry remains locked in the intense negotiations in Lausanne, where he was due to resume talks Sunday with Iranian Foreign Minister Mohammad Javad Zarif.
With French and German counterparts already in Switzerland, Chinese Foreign Minister Wang Yi and Russia`s Sergei Lavrov as well as Britain`s Philip Hammond were due to arrive later Sunday.
The ministers appeared Saturday to be narrowing in on a deal aimed at ending more than a decade of tensions over Iran`s nuclear ambitions and thwarting any drive to acquire an atomic bomb.
But Zarif said on his Facebook page late Saturday that the talks had become more complicated with the arrival of more foreign ministers.
"We have made progress towards an acceptable solution, but several important questions still remain," Zarif said.
Kennedy and Kerry had worked side-by-side in the US Senate for more than 25 years, before Kennedy`s death in August 2009. He had been the last surviving brother of late US president John F. Kennedy.
Kerry sent warm wishes to Ted Kennedy`s widow, Vicki, and praised the dedication of the new Boston institute which will seek to educate the public about the role of the US Senate in American politics.
"It is a vital element of our country`s government, and the EMK Institute will help Americans young and old understand it. That will be a profound legacy for Teddy," Harf added in a statement.