A grueling day of talks Wednesday between senior American, Iranian and European diplomats produced no breakthrough agreement on curbing Iran’s nuclear program, but officials said they still aim to reach a deal by the Nov. 24 deadline.

Secretary of State John F. Kerry, Iranian Foreign Minister Mohammad Javad Zarif and European Union foreign policy chief Catherine Ashton met for a total of six hours stretching through most of the afternoon and late into the night at an exclusive hotel in the center of Vienna.

A senior State Department official characterized each step of progress in the talks as “chipping away” at complex, technical differences, with virtually every sentence requiring an appendix of further explanation.

“We continue to make progress, but there is still a substantial amount of work to be done,” said the official, who spoke on the condition of anonymity to discuss the difficult and secretive negotiations.