(Adds quotes background)

ANKARA, April 9 (Reuters) - Iranian Supreme Leader Ayatollah Ali Khamenei on Thursday demanded that all sanctions on Iran be lifted as soon as a final agreement with world powers on curbing Tehran's nuclear programme was concluded.

In a live speech on Iranian state television, Khamenei said he neither backed nor rejected an interim accord reached between Iran and the powers last week. Its details would be decisive, he said, making his first comment on the framework deal.

The publication of a U.S. fact sheet showing terms that were at variance with the Iranian view of the agreement showed "devilish" U.S. intentions, he said.

"I neither support nor oppose it," he said. "Everything is in the details; it may be that the deceptive other side wants to restrict us in the details."

"The White House put out a statement just a few hours after our negotiators finished their talks...this statement, which they called a 'fact sheet', was wrong on most of the issues."

The tentative accord, struck on April 2 after eight days of talks in Switzerland, clears the way for a settlement to allay Western fears that Iran could build an atomic bomb, with economic sanctions on Tehran being lifted in return.

Khameni reiterated Iranian denials that Tehran was seeking to build a nuclear weapon.

He added: "What has been achieved so far does not guarantee a deal or even that the negotiations will continue to the end."

"I was never optimistic about negotiating with America... nonetheless I agreed to the negotiations and supported, and still support, the negotiatiors."

He said he supported a deal that preserved the "interests and honour" of Iran and that an extension of a June 30 deadline should not matter. (Reporting by Parisa Hafezi, additional reporting by Sam Wilkin in Dubai, Writing by William Maclean, Editing by Angus MacSwan)