>> reporter: nbc's ali arousi was in the crowd tonight. >> reporter: you never see these things. people are overjoyed! >> reporter: but it is real. there is no faith the iran irani regime can or will change, deal or no deal. >> people are celebrating because they got everything they wanted and the west got nothing at all. >> reporter: netanyahu said as far as the west is concerned, they messed up. >> a deal with the foremost sponsor of international terrorism. >> reporter: israelis worry they'll have to pay the price if this diplomatic gamble doesn't work. >> i think he made a big mistake. obama made a big one. but no one can do nothing. he decided and he was so determined in this mission. >> reporter: the israeli government couldn't stop the deal in vienna but it's hardly giving up. the next step is to use israel's friends and supporters to spike the deal in washington. an official in tel aviv said the next deal will be in washington. while israel has been by far the most vocal critic arab states especially saudi arabia, are also skeptical. they worry that iran will cheat and th

we began with ali arousi. tell us about this deal especially with president rouhani talking about this being a great deal and celebrations already beginning there tonight. >> reporter: it means an awful lot to the iranian people. they voted for rouhani to bring iran out of the cold and preserve sanctions and it looks like he did exactly what they wanted. a big celebration there, even last week the ministry said the celebrations are strictly forbidden. they're organizing gatherings so people here are ecstatic. and the reason they're ecstatic is because the last few years, even decades, have been especially difficult for them. sanctions have been put on them. they wanted to be able to travel. they wanted people to come to iran as tourists and that has not been on the picture for a long time and now they think that's going to happen. it's going to be a huge key change for people in iran. when people go on president obama wanted iran to feel more than iranians feel. if this deal didn't happen it really wouldn't af