WASHINGTON (Reuters) - President Barack Obama on Tuesday said he will "not countenance" Iran getting a nuclear weapon and criticized Republican presidential candidates for their "casualness" in talking of a possible war with Tehran.

Obama, at a news conference a day after meeting with Israeli Prime Minister Benjamin Netanyahu, said there was a window of opportunity to settle the dispute with Iran over its nuclear program diplomatically.

(Reporting By Tabassum Zakaria; Editing by Sandra Maler)