Seymour Hersh began reporting on this in 2006, I believe, and the diplomatic cables confirm plans to carry out regime change in Iran. Rawstory has some exclusive reporting.

According to a diplomatic cable released by WikiLeaks, in August 2007 the head of Israel’s intelligence agency urged US Under Secretary of State for Political Affairs, R. Nicholas Burns, to join with Israel in carrying out a five-part strategy to implement regime change in Iran.

Mossad Director Maier Dagan acknowledged at the meeting that the American analysis of Iran’s alleged nuclear weapons program was different from Israel’s, but he insisted that the threat from Iran was “obvious” and stated that Israel was willing to take action unilaterally.