U.S. Secretary of State John Kerry has cancelled plans to return to the United States for an event honoring Edward Kennedy in order to remain at the ongoing Iran nuclear talks in Switzerland.
The State Department said that "given the ongoing nuclear negotiations in Switzerland, the secretary regrets he will not be able to share this special time with them in person."
Kerry served in the Senate with Kennedy for nearly 25 years and the two were close friends.
Kerry's decision comes as the talks appear to have hit obstacles ahead of a March 31 deadline.
The State Department said late on March 28 that "serious but difficult work" remained for negotiators and that the pace of talks expected to intensify as "we assess if an understanding is possible."