UNITED NATIONS (Reuters) - Iranian Foreign Minister Mohammad Javad Zarif joined nuclear talks with six world powers on the sidelines of the United Nations General Assembly on Thursday, taking a seat next to U.S. Secretary of State John Kerry.

Thursday's meeting was the first between a top U.S. diplomat and an Iranian foreign minister since a brief encounter in May 2007, and came amid a charm offensive by new Iranian President Hassan Rouhani that has raised hopes for easing more than three decades of estrangement between Washington and Tehran.

(Reporting By Brendan McDermid and Michelle Nichols, writing by Matt Spetalnick)