Iranians walk by murals on the wall of the former U.S. embassy in the Iranian capital Tehran on Aug. 7, 2018. (AFP photo)

TEHRAN, Aug. 13 (Xinhua) -- Iran will never enter a new round of talks with the United States over the 2015 nuclear deal as Washington is "bullying and cheating" in negotiations, Iran's Supreme Leader Ayatollah Ali Khamenei said Monday.

Khamenei's remarks came in response to the recent U.S. gestures for unconditional renegotiation of the 2015 landmark Iranian international nuclear deal after its astounding withdrawal in May.

Tehran will not again sit at the negotiation table with the "cheating" U.S. government, Khamenei's official website said.

"Over the past 40 years, Americans have requested for negotiations for many times, but only met with Iran's negative answers," he was quoted as saying by Press TV.

"During negotiations, Americans only give promises using apparently assuring words, but want real concessions from the opposite side and do not accept promises," he said.

Negotiations with the United States at the present time will certainly be to Iran's disadvantage and are "forbidden," the Iranian top leader noted.

"We can only embark on negotiating with the United States after we reach the economic, political and cultural power that we have in mind so that the U.S. pressures and ballyhoo would not be able to affect us," he added.

Earlier in the day, Iranian Foreign Minister Mohammad Javad Zarif also said a recent proposal by the United States to enter into negotiations with Iran over Tehran's nuclear issue while re-imposing sanctions against the country is nothing but propaganda.

"Iran will never change its policies in the region under the U.S. sanctions and pressure," Zarif was quoted as saying by state TV.

"Iran will also never hold negotiations about its missile program, because our missiles do not threaten anybody," he added.

A day earlier, Zarif dismissed reports that Iran has plans to talk with the United States on the sidelines of the upcoming UN General Assembly meeting.

On Friday, Majid Takht Ravanchi, Iranian deputy foreign minister for European and American affairs, also said he doesn't see "any reason" for talks between Trump and Iranian President Hassan Rouhani at the 73rd UN General Assembly meeting next month.

"What expectations could you have from a person who pulls out from international engagement and now says let's hold talks," Ravanchi noted.

U.S. President Trump withdrew Washington from the 2015 Iranian nuclear deal, also known as the Joint Comprehensive Plan of Action, on May 8.

Since then, the Trump administration has slapped a number of sanctions on Iran while vowing to apply more.