The applause from Netanyahu’s boosters had barely subsided, however, before Obama administration officials fired back, arguing that the Israeli leader’s vision was recklessly unrealistic.

Many experts who closely track the Iran nuclear negotiations agreed that imposing major new demands or extending economic sanctions on Iran — the course advocated by Netanyahu — carries its own risks.

“There’s no guarantee that additional pressure on Iran at this time would lead to a better deal, or to Tehran giving up more of its nuclear infrastructure,” said Kelsey Davenport, director for nonproliferation policy at the nonpartisan Washington-based Arms Control Association. “What it risks doing is pushing Iran away from the negotiations and killing the prospects for a good deal that blocks Iran’s pathways to a nuclear weapon.”

Many observers said the spectacle in Washington did little to change minds of people familiar with the issue. “[A]s far as I can tell, there was nothing new,” President Obama told reporters shortly after the speech.

Israeli officials pointed to one tangible Netanyahu idea: that terms of a nuclear deal remain in place until Iran changes specific behaviors, such as supporting terrorist groups like Hezbollah or threatening Israel. Obama is currently considering agreeing to a deal that would expire, or “sunset,” at a specific time, perhaps in as little as 10 years.

“We can insist that restrictions on Iran’s nuclear program not be lifted for as long as Iran continues its aggression in the region and in the world,” Netanyahu said.

But Netanyahu offered few other specifics about how to wring more concessions from Tehran, frustrating Obama officials who feel that the Israeli prime minister — who faces national elections at home later this month — paints an unrealistic picture of what the negotiations can achieve.

For instance, Netanyahu did not endorse specific new economic sanctions against Iran, as have many members of Congress, though he did say that a better deal was possible through “keeping up the pressure on a very vulnerable regime.”

“Bibi’s view is you need to jack up the pressure,” says Robert Einhorn, a former Iran nuclear negotiator at the Obama State Department. But, Einhorn warns, America’s allies in the effort to prevent Tehran from acquiring a bomb have little appetite for extended or increased sanctions. Many have made economic sacrifices of their own by forgoing Iranian oil exports.

“In order to ratchet up the sanctions you have to have cooperative international partners,” Einhorn said, including big oil importers like China, Japan, South Korea, India and Turkey. “They’re the countries you have to convince to go beyond what they’ve already done. And it’s going to be very hard to convince them to squeeze Iran further if what we are demanding are concessions that these foreign partners would regard as unreasonable.”

Obama officials say that many foreign leaders share their view that for reasons of pride, politics and security, Iran — which has already devoted tens of billions of dollars to learning how to split the atom — will simply never relinquish a significant domestic nuclear program.

U.S. officials say it has already been a struggle to make some countries meet their commitments to reduce Iranian oil imports.

America’s European allies have also sounded a cautionary note. “New sanctions at this moment might also fracture the international coalition that has made sanctions so effective so far,” the foreign ministers of France, Germany, Britain and the European Union wrote in a January Washington Post op-ed. “Rather than strengthening our negotiating position, new sanctions legislation at this point would set us back.”

One senior Obama administration official argued that “it is not realistic that countries would take further economic hits in support of us” if America issued new negotiating demands. “The only reason they take the hit now by imposing sanctions is to force Iran to negotiate. If we make clear we are not really willing to negotiate, why would they go out on the limb?” the official added.

Israeli officials and some in Congress dispute that view, noting that the Obama White House has argued against previous congressional sanctions as counterproductive, only to later concede that they were helpful.

Some also argue that new sanctions aren’t necessary — so long as the current ones are given more time to work, with the accelerant of plunging oil prices that have squeezed oil-producing Iran’s budget.

Moreover, Obama officials and experts are concerned that Iran could match new demands from the U.S. by speeding up its nuclear activities. In a worst-case scenario, Iran would abandon the nuclear talks and throw out the international inspectors who provide visibility into the progress of its program.

Although Netanyahu disputed the notion that the alternative to what he called a “bad deal” is military conflict, many observers were skeptical.

“I don’t think we can get a deal on the terms that Netanyahu proposes,” Einhorn said. “He says the alternative to a bad deal is not war — it’s a better deal. That’s a good formulation. But what if the better deal is not achievable? What are you left with then?”