Washington ? President Barack Obama delivered his most explicit threat yet that the United States will attack Iran if that’s what it takes to prevent it from developing a nuclear bomb. At the same time, he warned Israelis they would only make a bad situation worse if they moved pre-emptively against Iranian nuclear facilities.

The double-barreled warning, in an interview published Friday, came before Obama’s high-stakes meeting with Israeli Prime Minister Benjamin Netanyahu on Monday and a speech Sunday to the American-Israel Public Affairs Committee, a powerful pro-Israeli lobby. Obama said an Israeli strike would stir sympathy for the Islamic republic in a region where it has few allies. But he made clearer than before that Iran could face attack from the United States.

“I think both the Iranian and the Israeli governments recognize that when the United States says it is unacceptable for Iran to have a nuclear weapon, we mean what we say,” Obama told The Atlantic magazine. “I don’t bluff.”

He said Iran and Israel both understand that “a military component” is among a mix of many options for dealing with Iran, along with sanctions and diplomacy, making plain a threat to attack that had previously been more subtly implied.

The warning reveals how the threat that Iran could pose to Israel has eclipsed every other issue in the close but often contentious U.S. relationship with Israel, and raised the political stakes for Obama. Iran’s disputed nuclear ambitions dwarf the unfinished business of peace with the Palestinians and Obama’s sometimes testy relationship with Netanyahu.