Western diplomats should expect Iranian militias to remain in Syria following the conclusion of a civil war that has roiled the region, according to a senior Russian diplomat.

Alexei Borodavkin, a Russian diplomat at the United Nations, made the remark in the run-up to U.N.-brokered negotiations intended to end the war. But his comments cast a shadow on the talks by repudiating key goals of the Syrian opposition groups who want Iranian militias to withdraw and embattled President Bashar Assad to relinquish power, despite his Iranian and Russian support.

"All this is very alarming and will hardly contribute to a constructive dialogue in Geneva," Borodavkin said Tuesday, per state-run media.

Russian President Vladimir Putin has tried to foster a competing peace process in Astana, Kazakhstan, where the talks could more likely be expected to produce a settlement that favors Russian interests. The United States, which supported opposition groups fighting Assad before focusing exclusively on the fight against the Islamic State in Syria, wants a U.N.-led process that could lead to Assad’s ouster and the withdrawal of Iranian forces from Syria.

Opposition leaders who attended a conference in Saudi Arabia adopted a similar view. "They also demand that Iranian militia units leave Syria, which is also unrealistic," Borodavkin said of the opposition leaders’ demands. "It is unclear how the opposition members plan to hold talks with representatives of the Syrian government if the delegation coming from [a conference in Saudi Arabia] views them almost as criminals with whom it is impossible to talk.”

Syria is strategically significant for all sides. Russia wants to maintain a naval base on the Mediterranean Sea, provided by the Syrian government. Iran wants its militias to be free to operate across Iraq and Syria, so the regime can coordinate directly with the Hezbollah terrorist group it supports in neighboring Lebanon. And Russia has helped Iran gain control of territory in Syria that is crucial to achieving that objective.

“Russia intensified its air campaign in early November 2017 in support of Iran’s strategic ground gains in Eastern Syria,” according to analysis from the Washington, D.C.-based Institute for the Study of War. “Russia has simultaneously used its support to Iran to limit the freedom of action of the U.S. Anti-ISIS Coalition and its allied Syrian Democratic Forces along the Euphrates River Valley in Eastern Syria. Russia and Iran are setting conditions to try and expel the U.S. from Syria and Iraq.”

U.S. lawmakers have long worried that Russia and Iran would make such an effort to diminish American influence in the Middle East. But it’s not just the United States that is concerned. Saudi Arabia and Israel, two major U.S. allies in the region, are increasingly alarmed that Iran-backed forces will pose a heightened threat to their nations if they gain enough military power in Syria.

Israeli Prime Minister Benjamin Netanyahu has warned Russia repeatedly that Israel will attack any Iranian forces that try to operate too close to the border of Syria and the Jewish state. "Iran is attempting to establish itself militarily in Syria," Netanyahu tweeted in August after a meeting with Russian Defense Minister Sergei Shoigu. "I told [Shoigu]: Iran needs to understand that Israel will not allow this."