TEHRAN, Sept. 16 (Xinhua) -- The Islamic republic will not negotiate with the United States over the existing issues under the U.S. sanction pressures, Iran's Government Spokesman Ali Rabiee said on Monday.

"Once, we negotiated (with the U.S.) under sanctions (to sign Iranian 2015 nuclear deal), but we will no longer negotiate under sanctions anymore," Rabiee told reporters.

"If (the U.S. President Donald) Trump gains our confidence and respects the Iranian nation, we will negotiate within the framework of P5+1 group," he said with reference to Iran's talks with five permanent members of the UN Security Council plus Germany over the former's nuclear program which resulted in the clinch of a landmark Iranian nuclear deal.

Trump withdrew the United States from the 2015 Iran nuclear deal in May 2018 under the pretext that the deal was not comprehensive.

Subsequently, the U.S. administration launched a "maximum pressure campaign" and reinstated sanctions on Iran's economy, mainly on Iran's oil exports.