WASHINGTON The No. 2 U.S. diplomat will travel to Vienna this week to take part in talks over Iran's nuclear program, the State Department said on Sunday.
In a statement, the State Department said Deputy Secretary of State Bill Burns would be among the U.S. officials taking part in the latest round of nuclear talks, which include six world powers and Iran and are scheduled for Monday to Friday.
The participation of Burns, who led secret U.S.-Iranian negotiations that helped bring about a Nov. 24 interim nuclear agreement between Iran and the major powers, could signal that the United States is intensifying efforts to break a logjam in the nuclear talks.
Iran, the United States, Britain, France, Germany, Russia and China set a July 20 deadline to reach a comprehensive agreement in an interim deal they reached in Geneva last November.
The latest round of negotiations in Vienna last month ran into difficulty when it became clear the number of centrifuges Iran wants to maintain was well beyond what would be acceptable to the West.
Iran says it needs to maintain domestic uranium enrichment capability to produce fuel for planned nuclear power plants without having to rely on foreign suppliers.
Some Western officials believe Iran will need many years to build any nuclear power stations and that its goal in enriching uranium is to be able to produce material for nuclear bombs, an allegation Iran denies.
Iranian President Hassan Rouhani urged the world powers on Saturday to reach a deal with Tehran by the July 20 deadline, arguing that sanctions meant to restrict its atomic activity had frayed beyond repair. He said the economic curbs had been softened by his government's policy of detente and would "not be rebuilt" even if no deal was reached.
(Reporting by Missy Ryan; Editing by Peter Cooney)