U.S. President Barack Obama delivers remarks on a nuclear deal with Iran at American University in Washington August 5, 2015. REUTERS/Jonathan Ernst Iran has been invited for the first time to participate in peace talks on Syria, in a move that recognizes Tehran as a legitimate stakeholder in the future of a country well into its fifth year of civil war.

Russian officials reportedly extended the invitation, which Iran accepted Tuesday, after meeting with the US, Saudi Arabia, and Turkey last week to discuss diplomatic solutions to the conflict. Officials in Washington have insisted the move was a “genuine multilateral invitation."

But some experts are wary that the invitation represents a concession to Iran's quest for regional hegemony and legitimizes its militant proxy, Hezbollah, by extension.

"By allowing Iran to participate in these talks, the US is essentially saying that Iran has a legitimate stake in Syria," Tony Badran, a researcher at the Foundation for the Defense of Democracies, told Business Insider. "But Iran's only stake in Syria is maintaining its bridge to Hezbollah in Lebanon."

Michael Pregent, an adjunct fellow at the Hudson Institute, echoed this sentiment.

"The invitation legitimizes Iran's involvement [in the war] and gives them a vote along with Russia to keep Assad in power," Pregent, a terrorism analyst and former US Army intelligence officer in Iraq, told Business Insider.

He added: "It also puts them in a position to ask for more concessions from the US and legitimizes Hezbollah by extension — a relationship that violates existing sanctions and should disqualify Iran and leave them uninvited."

'A valuable and irreplaceable tool'

A demonstrators hold up a flag of Lebanese Hezbollah and a picture of Syrian President Bashar al-Assad during a demonstration to mark the 60th anniversary of Khaled al-Hariri/Reuters As Iran's most crucial ally in the region, Syrian President Bashar Assad is critical to Iran's retaining its bridge to Hezbollah in Lebanon and preserving its geopolitical influence along the eastern Mediterranean.

"It is unlikely that the US or anyone else will be able to talk Tehran out of supporting Hezbollah from Syria or dropping its support for Bashar al-Assad," Frederic Hof, a senior fellow at the Atlantic Council and a former special advisor for transition in Syria under former Secretary of State Hillary Clinton, told Business Insider by email.

He added: "Iran considers Assad to be a valuable and irreplaceable tool in the context of Hezbollah, and considers him personally to be the heart of a supportive and even subordinate regime."

When UN Secretary-General Ban Ki-moon invited Iran in January to participate in a new round of Syria talks, uproar ensued.

US officials strongly objected, on the grounds that Iran had not accepted the terms for the talks — namely, that all parties work to establish "by mutual consent" a transitional body, sans Assad, to govern Syria. The UN secretary general was forced to withdraw the invitation.

Qassem Soleimani, leader of the Iranian Quds Force and IRGC commander, takes a photo with Syrian and Hezbollah forces in the Golan near the border with Israel. The Long War Journal

That Iran has been invited to the talks now, with no major objections, reflects a broader shift in how the US and its partners have come to perceive Assad's future — a shift that has been spearheaded, Badran said, by President Barack Obama.

"I don't see Iran's invitation to the talks as a change in the administration's policy — rather, it is in line with Obama's long-held perception of Syria as an Iranian sphere of influence, and his desire to legitimize Iran as a regional interlocutor of the US," Badran said.

"Indeed, that was the whole point of the Iran deal — to establish a broader regional partnership with the Iranians. Giving Zarif a seat at the table is just the logical continuation of that policy."

The hard part of getting Iran to the table, Badran noted, has been dragging in the naysayers like Saudi Arabia — which has a fierce regional rivalry with Iran dating back to 1979 — and Turkey, which has long been one of the Assad regime's staunchest opponents.

US Secretary of State John Kerry (L) sits across from Iranian Foreign Minister Javad Zarif (R) as negotiators wait for a meeting at the Beau Rivage Palace Hotel March 27, 2015 in Lausanne. Brendan Smialowski/Pool/Reuters At a joint news conference in Ankara on October 15, Saudi Foreign Minister Adel al-Jubeir and his Turkish counterpart, Feridun Sinirlioglu, told reporters, "We are in agreement that Bashar Assad has no role" in Syria's future. One week later, Saudi officials accused Iran of "occupying Arab lands" in Syria.

But Russia's intervention in Syria has escalated the conflict to a point at which, if Saudi Arabia or Turkey were to sit out of the talks, they might be viewed as standing in the way of finding a peaceful solution.

"Obama's vision has always been based on integrating rather than keeping out, and he has never wanted to be on a war footing," Badran said. "So he's leveraging the Russian intervention to get the Saudis and Turks to agree to Iran's involvement, and thereby accept a political framework that — at least temporarily — includes Assad."

"Diplomatically, Iran's involvement has cornered the few remaining backers of the Syrian revolution," Badran added.

'Does Iran even want this?'

As The Soufan Group noted on Wednesday in an intelligence brief, Iran and Russia will likely insist on a "metric-based" deadline for Assad to step down — that is, he will leave when he and his allies decide that they have effectively defeated extremism in Syria.

The US and its partners, on the other hand, will advocate a fixed timeline for his departure. Turkey has already suggested a deadline of six months.

It therefore remains to be seen whether the talks yield anything productive, or whether they serve to entrench the political gridlock even further.

"Iran said 'give us more' at every turn when the nuclear deal was being negotiated," Badran said. "So they may end up playing the same game at the Syria talks — especially since Washington has stated openly that it wants to avoid a regime collapse in Syria."

"For all intents and purposes, the US is already playing on Russian and Iranian turf."

Russia's President Vladimir Putin (R) shakes hands with his Iranian counterpart Hassan Rouhani at the welcoming ceremony during a summit of Caspian Sea regional leaders in the southern city of Astrakhan, September 29, 2014. REUTERS/Alexei Nikolsky/RIA Novosti/Kremlin Hof, on the other hand, provided a more cautiously optimistic outlook of the talks — if Iran is serious.

"What Tehran might be willing to do — and this would have to be tested — is to persuade Assad to abandon mass civilian homicide as the essence of his survival strategy," Hof said. "If civilians are taken off the bullseye, the prospects for a useful Syrian dialogue will increase and the ability of ISIS to recruit — inside Syria and around the world — will decrease."

He added: "Does Iran want even this? If discussions take place, I imagine American diplomats will try to find out."