Both President Obama and Secretary of State Kerry hit positive notes in their messages. But Iran's Supreme Leader Khamenei was critical of other elements.
Israeli Defense Minister Moshe Yaalon says Israel is on its own in facing the threat from Iran. Previously, he opposed a unilateral Israeli strike.
Iran has assured skeptical diplomats that it is slowing its nuclear work. The latest report from the UN nuclear agency backs them up.
The US and Iran have attacked each other in public to sell nuclear talks to skeptical audiences at home. But harsh words have eroded trust.
The Obama administration had previously used 'dismantle' to describe a final deal on Iran's nuclear program, but this went down badly with Iran. Obama said he would veto any new sanctions.
The UN announced Sunday that it had invited Iran to attend Syria peace talks in Geneva. The unexpected decision could scuttle the long-awaited meeting.
Iran turned down a limited US invitation to the Syria peace conference, but the two have an increasingly common interest in stemming the rise of Sunni militancy in places like Iraq.