The US has reversed longstanding opposition to Iran’s participation in peace talks to end the Syrian civil war, paving the way for a possible diplomatic breakthrough in the four-year conflict.

Officials in Washington insisted the move was a “genuine multilateral invitation” and implied they had succeeded in overcoming Saudi Arabian opposition to Iran attending the talks in Vienna on Friday.



Nearly two years ago, a similar offer for Iran to attend an earlier round of talks in Geneva was hastily rescinded by UN secretary general Ban Ki-moon after fierce opposition from the US, Britain and Syrian opposition groups.



But continued bloodshed and diplomatic stalemate have combined with a worsening refugee crisis and new Russian military intervention to put pressure on the international community to find a fresh political approach to ending the war.

The presence of Iran, which, along with Russia, has been a crucial ally of the Syrian government, could be a crucial factor in bringing the competing external players in the conflict to a common agreement on how to end the conflict.



The US insists that a central goal of the peace talks also remains the removal of current president Bashar al-Assad, who it says has been responsible for too many civilian deaths to remain a credible part of any future government.



“The ultimate goal that everyone wants to get to … is to come up with a framework for a successful political transition in Syria which leads to a government not led by Bashar al-Assad and that is representative of and responsive to the Syrian people,” State Department spokesman John Kirby told reporters in Washington on Tuesday.



But Washington officials did not say whether Iran had agreed to that principle too, who had extended the invitation, or even whether Iran would accept the invitation to attend this week’s Austrian talks.



“We anticipate that Iran will be asked to participate,” added Kirby. “Whether they come or not, that’s up to Iranian leaders.”



Nevertheless, an Iranian presence, which has not been seen in any previously failed peace talks on Syria, would be a significant breakthrough in itself, and a possible sign that the separate talks in Iran’s nuclear programme have succeeded in unlocking some of the most intractable fixed positions in the Middle East.



“It’s important for us to make sure that key partners are in these discussions,” added Kirby when asked about Iran’s participation at the Syria talks.



“The secretary [of state] wants to encourage these kind of discussions and conversations as we continue to look for solutions to what is a difficult political situation in Syria.”



Previously, the US has only hinted that Iran might play a role in the talks at some point in the future, but the Associated Press, which first reported the breakthrough on Tuesday, said that Saudi Arabia – which along with Turkey, Russia and the US has been holding talks on Syria – had relented after lengthy discussions including a direct plea by King Salman to John Kerry not to invite Iran in a meeting last weekend outside of Riyadh.

US officials refused to comment on other attendees at the talks, which may begin in preliminary form as soon as Thursday, but said they expected around a dozen participants in total.

One question is whether some Syrian opposition groups will refuse to attend if Iran is present, but the US called on them to “unify” their position.

“There’s going to have to be a role for the moderate opposition,” said Kirby. “They need to be more united and unified in their approach and the international community has an obligation to continue to work with them.”

The US would also not confirm whether Saudi Arabia, which has a fierce regional rivalry with Iran, would be there too but it implied that the decision to invite Iran had been reached jointly.

“All have had an opportunity to voice their thoughts about who should be participating,” said Kirby, who claimed the invitation was a “genuine multilateral” initiative.

The US also repeated its call on Russia to join in it as a “partner” in ending the conflict, something that Moscow claims it is doing by targeting the Islamic State with its airstrikes; Washington argues the strikes are so far more about propping up Assad.

Nevertheless, the decision to invite Iran represents a symbolic diplomatic victory for the Russians, who have always argued it was a mistake for the UN to rescind its earlier invitation.

Foreign minister Sergey Lavrov claimed that Ban Ki-moon’s decision to withdraw his last-minute offer in January 2014 also had a negative impact on the UN’s reputation as an independent arbiter in the conflict.

The bitter civil war is estimated to have killed at least 250,000 people and forced more than 11 million from their homes.