Former Mayor Edward I. Koch, who recently used the forum of a special Congressional election to broadcast his criticism of President Obama’s Israel policy, announced in an e-mail on Tuesday that Mr. Obama’s United Nations speech opposing the Palestinians’ bid for statehood had satisfied all his concerns, and that he was now prepared to support Mr. Obama’s re-election.

“Whatever rift existed before — and there was — that’s gone,” Mr. Koch said in a telephone interview. He said that he was now ready to go out and make the case to Jewish voters that the president deserved their support.

“He’s got me to go out there and persuade them,” he said. “I have shoes, will travel.”

Mr. Koch, a Democrat, had just a few months ago been so unhappy with Mr. Obama’s posture toward Israel that he endorsed the Republican candidate, Bob Turner, over the Democrat, Assemblyman David I. Weprin, in the Sept. 13 special election to replace Anthony D. Weiner in Congress. Mr. Turner won the race, in part thanks to votes from a sizable Orthodox Jewish community.

The Jewish vote was apparently influenced in part by Mr. Koch’s argument — made in automated telephone calls, news conferences and mailings — that Jewish voters could send a message to President Obama by voting against Mr. Weprin. After Mr. Turner’s victory, Mr. Koch threatened to continue raising his concerns on a national stage, suggesting that he would consider campaigning against Mr. Obama in battleground states like Florida.

But now that’s all over, Mr. Koch said Tuesday. He announced his change of heart in a weekly e-mail to supporters, in which he described attending a reception last Wednesday evening for United Nations delegates at the New York Public Library, hosted by the president and first lady.

Mr. Koch noted that the last time he was invited to such an event was when he was mayor and Ronald Reagan was president. In the e-mail, Mr. Koch wrote that Mr. Obama deserved praise for intervening to protect Israeli diplomats in Cairo and for providing Israel with military equipment and cooperation “far exceeding his predecessors.” He declared that he was “now on board the Obama Re-election Express.”

In the e-mail, he said that he thought that the outcome of the special Congressional election had influenced United States Middle East policy “in a positive way.” Asked by phone if he thought that result had actually changed Mr. Obama’s policy, he said he didn’t want to speculate.

“I like to think that what I did made common sense at the time, and I have no regrets in having done it, but that’s over, and I believe that it was helpful to the debate,” he said.

As for whether he and the president had discussed the special election, he said it hadn’t come up, and he “certainly wasn’t going to raise it,” because “one doesn’t do that.”

He declined to say what Mr. Obama had said in their interaction, but he did reveal that the president made a remark about one of the Republican presidential candidates, Gov. Rick Perry of Texas.

“I won’t say what he said,” Mr. Koch said, “but I said to him: ‘Mr. President, that’s the one guy you won’t have to worry about. Jews will never vote for anyone who doesn’t believe in evolution.’ ”

An Obama campaign spokesman did not respond to an e-mail seeking comment.