President Shimon Peres said on Sunday that Israel's reaction to landmark contacts between the United States and Iran had been too "scornful" of its key ally.
His comments came just hours after Prime Minister Benjamin Netanyahu left for Washington for talks with President Barack Obama, determined to expose what he described as "sweet talk" by Israel's arch-foe.
"You can agree or disagree (with the Americans) but I don't like this scornful tone," Peres told army radio.
"Other people have brains to think too, not just us. We should talk to them and try to influence them."
Netanyahu has been dismissive in his response to the drive by Iran's new President Hassan Rouhani to mend fences with the international community, which culminated in a historic 15-minute telephone conversation with Obama on Friday focused on Western concerns about Iran's nuclear programme.
Signup to our newsletter and follow us on Facebook and Twitter!
"I intend to tell the truth in the face of the sweet talk and charm offensive of Iran," public radio quoted the Israeli premier as saying as he boarded his plane for the United States.
"Telling the truth at this time is essential for world peace and security and, of course, for Israel's security."
Netanyahu is due to address the UN General Assembly on Tuesday, the same forum where last year he used a drawing of a bomb as a prop to underline how close he believed Iran was to being able to build one.
Israel, the Middle East's sole if undeclared nuclear-armed power, remains adamant that Iran is bent on developing a nuclear weapons capability, something it regards as a threat to its existence.
Israeli leaders have repeatedly vowed to take military action rather than see Iran develop a bomb and have called on its US ally to take tougher action against Tehran, saying they see no real change of policy under Rouhani.