The remarks highlighted the growing gulf and heightened tensions between the United States and Israel over the nuclear talks and other issues in the Middle East. But they also hinted at the limited tools left for Mr. Netanyahu, who is sidelined in the negotiations over Iran’s nuclear program, which he views as an existential threat to his country and has long made his primary focus.

As Washington and its Western allies increasingly show willingness to make some concessions to engage Iran in the negotiations, Mr. Netanyahu has few options beyond serving as the hawkish scold in hopes of applying pressure on Israel’s allies. “I don’t see any magic wand he can really produce at this moment,” said Dan Gillerman, a former Israeli ambassador to the United Nations. “This is a very difficult and trying time for the Israeli prime minister.”

Although Mr. Netanyahu’s declaration on Friday that Israel is not “obliged” by any agreement made in Geneva raised anew the specter of an Israeli military strike on Tehran, experts here say such an attack is all but impossible to imagine while negotiations proceed — and without American support.

Mr. Netanyahu could use Israel’s clout in Congress to push for new sanctions, or to foment discontent over President Obama’s foreign policy, but taking his case directly to Capitol Hill poisoned his relationship with the White House early on and could be too risky with the fate of Iran’s nuclear ambitions in the balance.