Despite U.S. President Barak Obama's statements indicating the United States has Israel's back in any military confrontation with Iran, a major chasm remains.

Washington is urging prudence and patience, while Tel Aviv says patience has its limits and time is running out to conduct pre-emptive military strikes on Tehran's nuclear enrichment sites.

"The United States is big and distant, Israel is smaller and closer to Iran, and naturally, we have different capabilities," Israeli Prime Minister Binyamin Netanyahu told Israel's Channel One television after talks with Obama in Washington. "So the American clock regarding preventing Iranian nuclearization is not the Israeli one. The Israeli clock works, obviously, according to a different schedule."

Israel, he said, must never be in a position where it couldn't defend itself.

Israel's position is understandable. Iranian leaders have repeatedly threatened to wipe Israel off the map and possession of nuclear weapons would bring that within their means. Iran is also in the process of moving its centrifuges for nuclear fuel enrichment to locations underground and within mountains, much more secure from aerial bombardment.

Washington's position is also understandable. Both the United States and the European Union have enacted economic sanctions that, once in effect, will severely hobble the Iranian economy as never before. The hope, of course, is that Iran will negotiate and abandon nuclear enrichment, which the West suspects is intended for the production of nuclear weapons.

Under the plans, EU countries will stop importing Iranian crude oil beginning this summer, while the United States will bar all international financial institutions having financial dealings with Iran from doing business with U.S. concerns.

Oil exports account for 80 percent of Iran's foreign exchange earnings and any drop would seriously affect the economy and the government's ability to fund social programs, including food subsidies.

On paper it sounds good but sanctions have seldom achieved the desired effect. Fidel Castro's communism still rules Cuba decades after U.S. sanctions were imposed; the breakaway British colony of Rhodesia survived international sanctions with the help of South Africa and under-the-table dealings with other African countries; and Saddam Hussein clandestinely sold oil despite a formal U.N. sanctions regime.

Tehran may well manage to get by with a little help from its biggest oil customers. With the prospect of the U.S. blockage of financial transactions with Iran crippling it from receiving payment in dollars from customers for its oil, reports indicate at least two of its prime customers -- China and India -- are exploring other methods of payment, including barter arrangements for good as payment.

Reports suggest Tehran's potential saviors, however, aren't necessarily acting magnanimously. Both are said to be demanding stiff price discounts for their help.

And then there is the question of how far Iran will comprise. Earlier negotiations over its nuclear enrichment program collapsed. And although it has indicated it's willing to return to the negotiating table, it has also made it plain that scrapping enrichment wouldn't be a subject for discussion, which would make such talks a venture in futility for the West.

The Obama position is also understandable from a domestic U.S. perspective. Any military conflict, no matter how short-lived, will cause economic hardship due to disruption of oil supplies from the region and the repercussions it would have on Obama's re-election bid.

Israel sees a direct threat to its existence coming from Tehran. But even its ability to act unilaterally is hindered. Its aircraft would probably need in-flight refueling and to destroy facilities already buried, it would need large bunker-busting bombs from the United States.

Netanyahu requested such bombs during his visit to Washington but the outcome of the request is unknown.

During the Vietnam War, the chant on U.S. streets was "just give peace a chance." And the nation, fed up with war, did just that. It signed a peace treaty with North Vietnam, which quickly ignored it and rolled south into Saigon. The South Vietnamese request for U.S. bombers to thwart the drive was ignored.

Today, with the nation sick of war in the Middle East, the White House is chanting give sanctions a chance.