While White House spokesman Jay Carney said on Monday that the Obama Administration still believes that there is "time and space" for a diplomatic track, coupled with sanctions, to succeed in convincing Iranian leadership to stop the nuclear program, Israeli Ambassador to the U.S. Michael Oren stressed in an interview to MSNBC that the Israeli clock "is ticking faster."

Ambassador Oren said Israel appreciates Secretary of Defense Leon Panetta's reiteration that the U.S. is determined to prevent Iran from acquiring a nuclear weapon, but mentioned the "structural differences between the United States and Israel which we can't ignore."

"The United States is a big country with very large capabilities located far from the Middle East," Oren said. "Israel is a small country with certain capabilities located in Iran's backyard. And Israel, not the United States, is threatened almost weekly, if not daily, with annihilation by Iranian leaders.

"We've now had five months of diplomacy," Oren continued, adding that the attempts to get Iran to negotiate an end to its nuclear program "haven't worked." 

"We still believe that truly crippling sanctions together with a credible military threat - and that I stress, that's a threat; not that we just say that it's credible, the folks in Tehran have to believe us when we say that - may still deter them. But we also have to be prepared, as President Obama has said, to keep all options on the table, including a military option," Oren said.

Meanwhile, Russia sharply criticized new U.S. sanctions against Iran, saying the measures to punish banks, insurance companies and shippers that help Iran sell its oil would harm Moscow's ties with Washington if Russian firms are affected.

Russia, which has long opposed sanctions beyond those approved by the UN Security Council to pressure Tehran over its nuclear program, called the measures "overt blackmail" and a "crude contradiction of international law."

The United States ceased most trade with Iran many years ago and has put increasing pressure other countries to reduce their business with the Islamic Republic.

The measures approved by Congress on August 1 build on oil trade sanctions signed into law by Obama in December that have prompted Japan, South Korea, India and others to slash purchases of Iranian oil.