Think of it as Ed Koch 3.0. It means Barack Obama can expect a New York headache any day now.

The Democrat and former mayor led the charge to elect a GOP congressman last year to protest Obama’s policy toward Israel, only later to make peace with the president and endorse him. Now he’s back on the warpath.

“I’m pissed,” he told me. “I’m not off the bus yet, but I’m pissed and I’m going to harangue them.”

The anger has a familiar, even circular ring: Obama’s making America look like a paper tiger in the face of Islamic violence, and his policy toward Israel is wrong. Obama’s refusal to meet last week with Prime Minister Benjamin Netanyahu is “unacceptable.”

“There should be a certain courtesy involved,” Koch said. “You don’t just say we can’t fit him into our schedule.”

The 87-year-old Koch, who recently got out of the hospital, is also upset that “nobody has adequately explained to me how the boos for God and Israel at the Democratic convention were louder than the cheers. How can that be?”

(My answer: That’s the sound of the new Democratic Party.)

In short, his list of gripes is long. So long that I am not the first to ask why he backs Obama. With Iran moving closer to a nuke, and Obama signaling to Iran that America will have nothing to do with an Israeli attack, the president’s position is hardening against our ally.

Moreover, Obama’s refusal to say directly that the Libya attack was terrorism, on the 11th anniversary of 9/11, is more than semantics. He can’t admit the obvious truth because it shreds his claim that his policy is working. Every burning American flag is a slap to his hubris.

Koch sees all that but is sticking for now because he agrees with Obama on abortion, taxes and Medicare.

But his ire is growing, with the murder of our ambassador a very sore point. At a Rosh Hashana address to a Manhattan synagogue, Koch said, “Any other self-respecting country where their embassy was attacked, their ambassador and his security detail murdered and the local police ran away would withdraw their embassy immediately in protest,” according to the Israel National News.

He urged that the United States suspend foreign aid to Egypt and other countries that fail to protect our embassies — and got “thunderous applause” from the congregation, the published report said.

The now-shaky honeymoon with Obama started after Koch helped to elect Bob Turner to the Brooklyn-Queens seat vacated by the disgraced Anthony Weiner. To reconcile, the president invited Koch to the White House for a 30-minute chat — “he talked for 20 minutes; I got 10,” he said.

They discussed Obama’s demand that Israeli-Palestinian negotiations start from the 1967 borders, an approach Koch believes can’t work. He also complained that Obama hadn’t made demands on Hamas, which rejects Israel’s right to exist.

“He’s a charming guy and very convincing,” Koch said, adding that he issued his endorsement soon after “because there’s no sense dragging it out once you’ve made up your mind.”

He followed by trumpeting his support in an op-ed column in a newspaper in Florida, a swing state where Jewish voters could make the difference. He hasn’t been asked to do another and sounds as if he might refuse unless the president changes course.

Except for African-Americans, Jews are the most reliable Democratic bloc. They give about 75 percent of their votes to the nominee, and Obama did slightly better in 2008. Some polls suggest his numbers are falling, and Koch sees an opening to get his attention.

A top priority is that Obama tell Iran that any attack on Israel would be seen as an attack on the United States. That way, Koch says, the red lines Netanyahu wants “aren’t necessary.”

He also worries that voices on the far left, including New York Times columnist Bill Keller, are arguing that a nuclear-armed Iran could be contained.

“That’s Munich all over again, and Israel would be Czechoslovakia,” Koch fumed.

But he stresses again he’s still with Obama.

Subject to change, I ask?

“Of course,” he fires back.

To read more from Michael Goodwin on additional topics including Time magazine, click here