(Reuters) - Iranian Supreme Leader Ayatollah Ali Khamenei on Thursday demanded that all sanctions on Iran be lifted at the same time as any final agreement with world powers on curbing Tehran's nuclear program is concluded.

Khamenei, the Islamic Republic's most powerful figure and who has the last say on all state matters, was making his first comments on the interim deal reached last week in the Swiss city of Lausanne.

He repeated his faith in President Hassan Rouhani's negotiating team. But in remarks apparently meant to keep hardline loyalists on side, he warned about the "devilish" intentions of the United States.

"I neither support nor oppose the deal. Everything is in the details, it may be that the deceptive other side wants to restrict us in the details," Khamenei said in a speech broadcast live on state television.

His stand on the lifting of sanctions matched earlier comments by Rouhani, who said Iranwould only sign a final nuclear accord if all measures imposed over its disputed atomic work are lifted on the same day.

These include nuclear-related United Nations resolutions as well as U.S. and EU nuclear-related economic sanctions.

"All sanctions should be removed when the deal is signed. If the sanctions removal depends on other processes, then why did we start the negotiations?" Khamenei said.

The U.S. State Department on Thursday repeated its position that sanctions against Iranwould be removed gradually.