Speaking to reporters in Tehran on Friday, Majid Takht Ravanchi said Iran will press ahead with the nuclear talks in order to achieve the desirable result.
"There is no deadline for the nuclear negotiations from the viewpoint of Iran," he stressed.
The Iranian deputy foreign minister said the bulk of a comprehensive nuclear agreement and its annexes have been finalized, and only a few "key points" have remained to be negotiated.
Takht Ravanchi underscored that the onus is on the other side to "make tough decisions" if it really seeks to reach a deal.
They have to choose between an agreement and the sanctions, he went on to say.
Diplomats from Iran and the Group 5+1 (Russia, China, the US, Britain, France and Germany) are engaged in tight diplomatic meetings in Vienna to clinch a lasting deal on Tehran's nuclear program.
Over the past two weeks, they have twice extended deadlines for completing a long-term nuclear agreement.
Negotiators have given themselves until the end of the day on Friday.