WASHINGTON-A senior U.S. official says that negotiations to allow Greek citizens to travel to the United States without visas are back on track.

Department of Homeland Security Assistant Secretary Richard Barth had previously said that the talks had been set back after Greek officials backed out of a draft agreement in April.

He said in May that the breakdown had moved Greece behind other countries in talks with the United States to join the visa-waiver program.

He said Wednesday that Greece could join the program by the end of the year.