Moshe Yaalon, whose remarks were reported in the Haaretz daily on Tuesday, caused friction with the United States only two months ago when he described Secretary of State John Kerry's quest for Israeli-Palestinian peace as messianic and obsessive.
His latest comments, confirmed by an Israeli official who was present at lecture Yaalon delivered at Tel Aviv University on Monday, displayed deep disappointment with U.S. President Barack Obama's handling of current world issues.
"We had thought it would be the United States that would lead the campaign against Iran," said Yaalon, who pointed to the Ukraine crisis as an example of Washington "showing weakness".
It was unclear from Yaalon's reported remarks where he believed the United States had gone wrong on Ukraine.
Iran and six world powers will try to make headway on the nuclear dispute in talks that started in Vienna on Tuesday, with Western officials hoping to find final agreement over the case.
Angry with the massive progress over Iran’s negotiations with the Western countries over its peaceful nuclear issue, Yaalon said "Therefore, on this matter, we have to behave as though we have nobody to look out for us but ourselves."
"Unfortunately, when it comes to negotiating at a Persian bazaar, the Iranians are better," claimed Yaalon.
In the Middle East, Yaalon also said, he had heard "voices of disappointment" over a lack of U.S. support for the foreign backed terrorist groups in the three-year-old conflict in Syria.
And on a recent visit in Asia, he added, he found "disappointment about China getting stronger and the U.S. getting weaker".
He has demanded that any final accord dismantle Tehran's uranium enrichment centrifuges, a position at odds with Obama's suggestion that Iran, which says its nuclear program is peaceful, could be allowed to enrich on a limited basis for civilian purposes.
"Comfortable Westerners prefer to put off confrontation, if possible to next year or the next leadership term. But in the end, it will blow up," Yaalon said, referring to probable final nuclear deal of the West with Iran.