Asked to comment on media reports alleging that the US has sent a letter to Tehran with a specific date as deadline for Iran's response, Ahmadinejad said, "They have probably specified a deadline for themselves, because basically they don't have the right to decide our fate."
"We oppose such a literature," President Ahmadinejad reiterated.
Earlier, Iranian Foreign Ministry Spokesman Hassan Qashqavi dismissed media reports that the US has set an October deadline for the completion of the first round of talks with Iran on its nuclear program.
"We have not received such an announcement from official and political sources," Qashqavi told reporters in a weekly press conference here in Tehran on Monday.
Meantime, the White House rejected calls for establishing a timeline on its engagement with Iran, saying the process should be allowed to move forward.
Speaking to foreign journalists at the Foreign Press Center in Washington, National Security Council spokesperson, Mike Hammer, also acknowledged that Washington's efforts toward Tehran could "take some time".
"I think it's not appropriate at this time to be trying to establish timetables for this, but rather, to see how the engagement can move forward," Hammer said, dismissing an Israeli request from the US to set a time-limit on any nuclear talks with Iran.