Nightly News | January 31, 2012
>>> moving on tonight, u.s. intelligence has a chilling new assessment about the scope of the threat from iran . officials today told the u.s. senate they believe iran , anticipating an attack by israel or the u.s. or even both on its nuclear facilities , is now more willing to attack the united states at home and abroad. we get more tonight from our chief foreign affairs correspondent andrea mitchell .
>> reporter: intelligence officials told senators the first warning was last year's alleged plot to blow up the saudi ambassador at a washington restaurant. israeli officials say another attempt, a busted iranian plot in bangkok earlier this month, to blow up israel 's embassy and a synagogue.
>> a plot in october really did change, i think, the u.s. intelligence community 's views as to what iran was willing to do here in the homeland.
>> reporter: why would iran take such a risk? it feels threatened. three weeks ago, a fifth iranian nuclear scientist was assassinated in the streets of tehran. economic sanctions are beginning to bite hard, and israeli's leaders are signalling they think time is running out this year to stop iran from getting a bomb.
>> iran must not be allowed to develop nuclear weapons , period.
>> reporter: in fact, only days ago, the head of mossad, israel 's top spy, secretly briefed congressional leaders and the head of the cia.
>> israel does see this possibility as an existential threat to their country.
>> obviously, this is a very sensitive issue right now. we're doing a lot with the israelis, working together with them.
>> reporter: experts warn that the u.s. is even more vulnerable than israel if iran retaliates or launches a preemptive bomb plot.
>> israel is relatively small. getting at israel is hard to do. and it has very formidable defenses for it. america has assets and vulnerabilities around the world.
>> reporter: soft u.s. targets like embassies throughout the persian gulf . and 90,000 american troops in afghanistan, next door to iran . still, intelligence officials told the senate today, they don't think iran has taken the final step, deciding to build a bomb. but israel does think iran has crossed that red line . and u.s. officials say if attacked, iran would not hesitate to retaliate against both israel and the u.s. andrea mitchell , nbc news, washington.