Any attempt to get the UN to go along with more stringent sanctions is a completely lost cause, as China (and possibly Russia) will veto sanctions, and Clinton knows that.
Any multilateral sanctions against Iran will almost inevitably lead to war; Clinton knows that also.
Israel may either create some kind of "false flag" incident to kick things off, or simply attack Iran unilaterally at first.
That, of course, will drag the US into the fray, because although Israel may well start such a military campaign, it cannot conclude such a campaign on its own without US military help.
Admiral Mullen, the Chairman of the US Joint Chiefs of Staff, was in Israel over the weekend, and made a statement to the effect that the US would always protect Israel.
Clinton understands this also.
But threatening the UN to go along with sanctions because Israel may attack Iran is a very dicey tactic for the following reasons.
1. Iran is a signatory to the NNPT.
2. Consistent inspections of Iranian nuclear facilities have revealed no missing nuclear material, nor the level of uranium enrichment necessary to create a bomb. Yes, they are enriching uranium to 20% for medical isotopes. But weapons-grade uranium must be enriched to over 90%, which is not happening.
3. Israel has nuclear weapons, as confirmed by the revelations of Mordechai Vannunu, former Israeli Prime Minister Olmert, and former US President, Jimmy Carter.
4. Israel refuses to become a signatory to the NNPT, and consequently, there are no IAEA inspections of their nuclear facilities.
So what we have here is a threat by a rogue nation (Israel) to attack Iran, which is playing by all the NNPT rules unless the UN issues sanctions against Iran?!?
What's wrong with this picture?!?
And just as a little side note, the US is violating its own laws by giving any military and financial aid to Israel.
There's a law on the books called Symington Amendment, which forbids the US from giving any aid to any country which has nuclear weapons, but is not a signatory to the NNPT.
Chew on that one for a while as you're filling out your tax paperwork this year, with the understanding that the US gives 3 billion dollars every year in aid to Israel!