LONDON, June 6 (Reuters)

A facility in Iran's Natanz nuclear plant to build advanced centrifuges will be completed in a month, Iran's nuclear chief said on Wednesday, as Tehran prepares to increase its uranium- enrichment capacity if the nuclear deal collapses after U.S. exit.

"After the supreme leader's order we prepared this centre within 48 hours. We hope the facility to be completed in a month," Ali Akbar Salehi, the head of Iran's Atomic Energy Organisation, said on Wednesday on state television.

Supreme Leader Ayatollah Ali Khamenei said on Monday he had ordered preparations to increase uranium enrichment capacity if the nuclear agreement with world powers collapsed.

(Reporting by Bozorgmehr Sharafedin, editing by Larry King)