JERUSALEM—Iran is about a year away from developing a nuclear weapon and the U.S. remains committed to doing everything in its power to prevent that from happening, President Barack Obama said in an exclusive interview aired Thursday on Israeli TV.

Just days before he is to arrive in Israel for his first presidential visit, Mr. Obama told Israel's Channel 2 TV that while he still prefers diplomacy over force, but that a nuclear Iran is a "red line" and all options remain on the table to stop it.

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