White House political advisor Karl Rove, who masterminded US President George W Bush's political campaigns in 2000 and 2004, has said he will resign at the end of this month.

Mr Rove told The Wall Street Journal that he thinks 'it's time'.

The newspaper said Mr Rove's resignation as White House Deputy Chief-of-Staff would become effective on 31 August.

Mr Rove has been under fire since 2003, when retired US diplomat Joseph Wilson claimed he had illegally leaked to the media the identity of Mr Wilson's wife, Valerie Plame, a covert CIA employee.

Mr Wilson asserted the leak had been orchestrated in retaliation  for his New York Times article, in which he refuted the Bush administration's claim that Saddam Hussein had explored ways of purchasing uranium ore from Niger.

The claim, made by President Bush in his 2003 State of the Union address, was widely used to justify the subsequent invasion of Iraq.

An investigation into the leak led to perjury and obstruction of justice charges, and subsequent conviction of Lewis 'Scooter' Libby, former chief of staff for Vice President Richard Cheney.

But prosecutors determined last year there was no reason to charge Mr Rove with any wrongdoing.

Although not directly involved in foreign policy decisions, Karl Rove has been widely reported to have played a key role in persuading US Congress to endorse the March 2003 invasion of Iraq.

A White House spokesperson described the departure as a big loss.