Sunday Times: Israeli plans nuclear strikes against Iranian nuclear program

Revealed: Israel plans nuclear strike on Iran - Sunday Times - Times Online

Of course, these reports may also be part of a psychological warfare campaign, but I see no reason to discount Israel's intent to prevent Iran to develop nuclear weapons. For every action, there is a reaction, and it is not hard to imagine a concerted and very damaging Iranian response.
From the standpoint of the U.S., the immediate problem is Iraq. The dilemma is that an added increment of 20,000 or more U.S. soldiers can be relatively easily outbid by an increase in support for insurgents. Iran's incentives for providing that support are quite obvious, especially since keeping the U.S. bogged down in Iraq is something of an antidote to Israel's leaked threats to strike Iran.
This is a multilevel chess game and the U.S. is still playing checkers.