"I couldn't comment either way," spokeswoman Dana Perino said after The New Yorker magazine reported tat the US Congress passed US President George W. Bush's funding request for a dramatic increase in such secret operations.

Asked about the likelihood of US military action against Tehran's disputed nuclear program before the president leaves office in January 2009, Perino said Bush "is singularly focused on trying to solve this issue diplomatically."

The New Yorker, which cited former military, intelligence and congressional souces, said the funding revealed a "major escalation" in clandestine operations aimed at destabilizing the Islamic republic's religious leadership amid concerns over Tehran's nuclear ambitions.

Among the methods being used are increased US support for minority and dissident groups and intelligence gathering about Iran's nuclear facilities, said the article, written and reported by Seymour Hersh.

Although such covert activities in Iran are not new on the part of the United States, the magazine said the "scale and the scope of the operations in Iran, which involve the Central Intelligence Agency and the Joint Special Operations Command (JSOC), have now been significantly expanded."

However, US ambassador to Baghdad Ryan Crocker on Sunday flatly rejected the allegation of cross-border operations from Iraq into Iran.

"I can tell you flatly that US forces are not operating across the Iraqi border into Iran," he told CNN television.

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