More fuel was added to the fire of speculation that Israel is poised to attack Iran when Prime Minister Benjamin Netanyahu demanded Sunday a "clear red line" that would convince Tehran that world powers are serious about stopping nuclear weapons, even at the cost of military engagement.

"The international community is not placing a clear red line for Iran, and Iran does not see international resolve to stop its nuclear program," the premier told his Cabinet in a public address. "Iran must not have nuclear weapons,"

These and other remarks by top Israeli officials, especially Defense Minister Ehud Barak, have led to widespread speculation that a strike on Iran would take place before the Nov. 6 U.S. elections, testing President Barack Obama on the longstanding Israeli alliance. Israeli officials have said they expect more resolve from the Obama administration to frustrate Iran's presumed nuclear ambitions.

Iran claims its enrichment program is for peaceful purposes, but it has hampered efforts to inspect facilities. It is widely accepted that Iran is enriching more uranium than would be necessary to feed its one reactor. The U.N.'s International Atomic Energy Agency said Thursday Iran has doubled the number of centrifuges at its facility in Fordow, south of the capital, to 1,000 in the past four months.

Experts, such as the Institute for Science and International Security and Eurasia Group, say Iran has faced delays in its program -- perhaps as a result of U.S. or Israeli sabotage.

White House Press Secretary Jay Carney told journalists after the IAEA report came out that the Obama administration has made it clear to Iran that diplomatic efforts by the West would not be open "indefinitely" and that it had limited time to stop refining uranium and to open its program to inspections.

Netanyahu's latest pronouncement comes after U.S. Chairman of the Joint Chiefs of Staff Gen. Martin Dempsey was quoted by The Guardian as saying an Israeli attack would not stop Iran's nuclear program, suggesting that the U.S. doesn't want to appear to be poised to cooperate with Israel in a unilateral military operation.

"I don't want to be complicit if they choose to do it," Dempsey said. The word "complicit" startled many Israelis.

"Dempsey's comments are strange in that they would seem to contradict the continual statements from the White House that the security and defense cooperation between Israel and the US has never been as close," a senior Israeli official told the Jerusalem Post in a report published Sunday.  

Chemi Shalev of the Israeli newspaper Haaretz said in his weekly column on Sunday that Obama should use his acceptance speech at this week's Democratic National Convention to allay Israeli concerns that the U.S. would force it to go alone to stop Iran from reaching the threshold of nuclear weapons capability.

"If I didn't know any better I would assume that the Chairman of the Joint Chiefs of Staff General Martin Dempsey is trying to goad Israel into attacking Iran," wrote Shalev. "Otherwise, why would he go to such great lengths to try and persuade them that Israel is on its own and can rely only on itself?"