Susan Walsh, Associated Press
U.S. State Department Under Secretary For Political Affairs Wendy Sherman testifies before the Senate Foreign Relations Committee on Capitol Hill in Washington, Tuesday, July 29, 2014.

WASHINGTON — The Obama administration's chief nuclear negotiator is meeting Thursday with Iranian officials in Geneva as negotiations resume on a deal to prevent the Islamic republic from developing nuclear weapons.

The State Department says Undersecretary Wendy Sherman will be part of a U.S. delegation that also includes Deputy Secretary of State William Burns.

Iran and six world powers failed last month to meet their target date for cutting a nuclear deal but agreed to extend the talks until November.

In testimony before the Senate Foreign Relations Committee, Sherman refused to provide a hard deadline for a deal with Iran.