Washington  - The world powers led by the United States will insist in a meeting Thursday with an Iranian delegation that Tehran immediately open its newly revealed nuclear plant to international inspectors, the Washington Post reported online.

The existence of the second Iranian nuclear facility was revealed Friday in an announcment by US President Barack Obama, who joined with leaders from Britain and France to accuse Tehran of concealing from UN inspectors the plant, which is believed to be intended for enriching uranium.

Citing administration officials in an article posted late Saturday, the paper said that the six countries heading into talks with Iran - the US, Britain, France, China, Russia and Germany - would also seek access to documents and people where the tunnel complex is being built.

The six countries are due to meet Thursday in Geneva with Iranian officials.

The Post's sources said that failure to give a serious response by the end of the year would bring a strong push for harsh economic and financial sanctions with the intention of crippling Iran's economy. (dpa)