WASHINGTON - In the face of mounting pressure from hawks in Washington and the continued threat of military action from Israel, the Barack Obama Administration has been taking a harder line in its latest pronouncements about Iran.

Recent media reports have suggested that the administration is leaning toward an end-of-September deadline for Tehran to respond to U.S. diplomatic outreach concerning its nuclear programme, at which point it will consider stepping up sanctions against the Iranian energy sector.

This course would cut against the advise of a growing number of Iran analysts, who have cautioned both that the Tehran regime is in no position to negotiate at the moment and that sanctions are likely only to solidify the power of Supreme Leader Ali Khamenei and President Mahmoud Ahmadinejad.

But the administration is facing a great deal of pressure to move quickly to sanctions from congressional hawks - backed by hardline organisations within the so-called "Israel lobby" - who have been pushing for a tougher line against Tehran since well before the Jun. 12 elections that triggered Iran's current political crisis.

While it remains too early to tell whether the Obama Administration intends to follow through on threats of sanctions before the end of the year, recent statements by administration officials have sounded increasingly impatient with the rate of diplomatic progress.

"We need to take stock in September," Secretary of State Hillary Clinton said Sunday in a television interview with CNN's Fareed Zakaria. "If there is a response, it needs to be on a fast track. We're not going to keep the window open forever."

Clinton also stated that the U.S. is working with allies to prepare "a very robust set of sanctions that we can get the international community to sign off on" in case engagement does not bear fruit.

The administration has suggested that a Sep. 30 U.N. General Assembly meeting will be the deadline for a diplomatic response from Tehran.

This end-of-September deadline is itself a testament to the political pressure the administration has come under from the right.

When Obama took office in January, he was reluctant to set an explicit timetable for engagement. During meetings with Israeli Prime Minister Benjamin Netanyahu in May, Obama eventually suggested that the administration would perform a "reassessment" of progress at the end of the year.

The turmoil that followed Iran's June elections has led some analysts to propose a pause in the engagement schedule - since Iran remains preoccupied with its internal crisis and its political situation fluctuates on a daily basis.

Instead, the engagement timetable seems, if anything, to have been expedited. While the administration has retained the end-of-year timetable for tangible diplomatic progress, the end-of-September deadline for a response is comparatively new.

Few expect Iran to be able to resolve its internal turmoil by Sep. 30, leaving open the question of how the U.S. intends to respond if the deadline passes without a response.

Trita Parsi, president of the National Iranian American Council (NIAC), is among those calling for a "tactical pause" in engagement. Parsi cautioned Monday on the Huffington Post that, "the biggest mistake the U.S. can commit is to begin setting deadlines that no one - including the U.S. itself - believes can be held up."

Hawks in Congress, however, have other ideas. Congressional leaders plan to push new anti-Iran sanctions legislation in September - barring any major change in the diplomatic situation.

The most prominent piece of sanctions legislation is the Iran Refined Petroleum Sanctions Act (IRPSA), which would impose penalties on firms exporting refined petroleum products to Iran. The IRPSA is co-sponsored by more than half the members of Congress.

Hardline "Israel lobby" organisations such as the American Israel Public Affairs Committee (AIPAC) and the Conference of Presidents of Major American Jewish Organisations are planning a major September lobbying push in support of the legislation, the Forward reported last week.

The Obama Administration has refrained from public comment on the IRPSA and other pending congressional legislation.

But, last week, a flurry of media reports suggested that the administration was giving increased consideration to new sanctions.

Israeli newspaper Ha'aretz reported Jul. 31 that U.S. National Security Advisor James Jones had briefed Israeli officials on U.S. plans for new sanctions. Similar reports in The New York Times and The Guardian soon followed.

However, these reports relied primarily on anonymous Israeli and European officials - leaving open the possibility that outside actors were leaking information in order to try to box the administration in to new sanctions.

In any case, all signs suggest that if the administration turns to sanctions, it will aim for multilateral sanctions in conjunction with allies rather than the unilateral sanctions being pushed by Congress.

"The coverage of the Obama Administration's stance on sanctions has been pretty disingenuous," NIAC Acting Legislative Director Patrick Disney told IPS. "I believe the administration has communicated that if Iran does not accept by the end of September the invitation to begin talks, then the U.S. will begin the process for another round of multilateral sanctions."

"[But] there is no evidence that the administration has communicated anything remotely supportive of the [petroleum] sanctions legislation to Congress," Disney added.

Proponents of petroleum sanctions claim that they will weaken the regime by exploiting its reliance on refined petroleum imports. Despite its natural oil reserves, Iran lacks refining capacity and must import between 25 and 40 percent of its refined petroleum.

Even some hawks concede, however, that unilateral sanctions measures such as the IRPSA would be of limited utility in depriving Iran of refined petroleum. Multilateral sanctions would be more effective - however most analysts are sceptical that Russia and China would sign on to such measures.

But, a growing number of commentators have suggested that even effective petroleum sanctions would be self-defeating. They argue that the brunt of these sanctions would be borne by innocent Iranian civilians rather than the regime itself, and that they would be likely to solidify the regime's power by allowing it to rally against a common enemy.

Sanctions opponents point to the example of Iraq, where strict sanctions imposed from 1990 to 2003 were blamed for hundreds of thousands of civilian deaths - without weakening the Saddam Hussein regime's hold on power.

"[T]here is absolutely not a shred of evidence that any major or even minor opposition leader - from [presidential candidate] Mir Hossein Moussavi to [presidential candidate] Mehdi Karrubi to [former president] Mohammad Khatami, or any of their related political organs or legitimate representatives - has ever uttered a word that could possibly be interpreted as calling for or endorsing any sort of economic sanction against Iran," wrote Columbia University professor Hamid Dabashi on CNN.com.

"As in the Iraqi case, imposition of economic sanctions on Iran will have catastrophic humanitarian consequences, while it will even more enrich and empower such critical components of the security and military apparatus as the Pasdaran and the Basij," Dabashi wrote.

On Tuesday, Nobel Prize-winning Iranian human rights lawyer Shirin Ebadi warned against sanctions because of the harm they would do to the Iranian people, Reuters reported.

Beyond the argument over sanctions looms the threat of Israeli military force. Israel has repeatedly signalled that it would consider a military strike against Iranian nuclear facilities if it is not satisfied with the progress of negotiations.

Some observers suggest that the Obama Administration's increased talk of multilateral sanctions is primarily intended to placate Israel and its hawkish allies in the U.S., thereby giving the administration some breathing room to work on a deal.

But these same hawks are determined to force the administration to follow through on its talk of sanctions, and matters seem likely to come to a head in the days leading up to the Sep. 30 deadline.