VIENNA — With only three days to go before a deadline to reach a nuclear accord to constrain Iran’s nuclear program, the talks here appeared to be marked by a heavy dose of brinkmanship on Friday as Iran’s top negotiator made clear he was leaving for Tehran to consult with the country’s leadership — only to reverse himself later in the day.

Iranian news agencies had reported that Mohammad Javad Zarif, Iran’s foreign minister, was returning to Tehran to seek further instructions. The State Department spokeswoman announced soon afterward that Secretary of State John Kerry would be leaving for Paris, where he would confer with European officials and stay in touch with Obama administration officials in Washington.

But Mr. Zarif later deferred his plans, telling Iran’s official IRNA news agency that “there were no remarkable offers and ideas to take to Tehran.” And that led Mr. Kerry to shelve his plan to leave, too.

American and European officials vowed to press on, and more high-level negotiating sessions were expected on Saturday. Yet the difficulties in the talks suggested it was unlikely that any agreement that might be announced on Monday would be a complete one and increasingly likely that an extension in the deadline would be needed.