WASHINGTON (AP) — The Obama administration has a vision for Syrian leader Bashar Assad’s departure. Even if it works, the president won’t be around to see the plan through.

An internal U.S. timeline for a best-case Syrian political transition, obtained by The Associated Press, sets a date of March 2017 for Assad to “relinquish” his position as president and for his “inner circle” to depart. That is two months after President Barack Obama leaves office and more than five years after Obama first called for Assad to leave.

Syria, according to the would-be American strategy, would hold votes for a new president and parliament in August 2017 — some 19 months from now.

The State Department said Wednesday the timeline was prepared late last year as a guide for Secretary of State John Kerry and other U.S. diplomats working on a political transition for Syria.

Spokesman John Kirby described the document as a “staff-level think piece” that is “preliminary and pre-decisional” and not “an official position.” He also said it is “not an accurate projection of plans by the international community to effect a political transition in Syria.”

However, many of the milestones mentioned in the document comport with the basics of the U.N.-endorsed plan. Other officials said they accurately reflected the administration’s thinking. One official, who like the others spoke on condition of anonymity to discuss the private document, said the goal for Assad to leave in March 2017 might slip even further.

Countless hurdles lie ahead for implementation of this latest outline for ending five years of conflict that has killed more than a quarter-million people, created the worst European refugee crisis since World War II and allowed the Islamic State group to carve out a would-be caliphate across parts of Iraq and Syria.

Not the least of those hurdles is the growing rift between Sunni-led Saudi Arabia and Shiite-ruled Iran, which back opposite sides in the Syria conflict and had to be lobbied heavily to agree to meet in Vienna to craft a way forward for the war-torn country. Saudi Arabia executed a prominent Shiite cleric and then severed diplomatic relations with Iran this week after its embassy in Tehran was stormed by a mob protesting the death.

It is not yet clear what impact those developments might have on the Syria negotiations.

If Saudi-Iranian tensions can be overcome, if peace talks between the Syrian government and opposition go ahead later this month as planned and if they are successful, the biggest challenge to the U.S. timeline is still that no one else has yet agreed to its specifics, particularly those related to Assad’s departure.

Assad has steadfastly refused to step down while his nation’s terrorist threat, as he sees it, persists. The timeline offers no explanation for exactly how Assad would leave or what his post-presidential future might hold.

And his chief backers, Russia and Iran, have resisted all efforts by outside powers to determine Syria’s future leadership, insisting that is a decision for the Syrian people. Russia and Iran may object to the U.S. timeline’s call for Assad to leave six months before elections would be held.

In addition, the Syrian opposition wants Assad out as soon as possible. The opposition along with U.S. allies like Saudi Arabia, Qatar and Turkey could view the American concept as a betrayal.

In recent months, Washington and its allies in European capitals have retreated from demands that Assad leave power immediately as the Islamic State gained territory in the region and the priority shifted to defeating the militant group.

The timeline, however aspirational, shows how U.S. diplomats and policymakers are determined to outline an exit plan for Assad and not let concerns over the Islamic State and other extremist groups allow him to cling to power indefinitely.

The document obtained by the AP starts Syria’s new political process next month. An 18-month transition period would be initiated, consistent with the plan endorsed by the U.N. Security Council last month. Government-opposition peace talks are to begin in Geneva on Jan. 25.

The U.S. timeline envisions the Security Council signing off on a framework for negotiations between Assad’s representatives and the opposition, leading to the formation of a security committee in April. That would be accompanied by an amnesty for some government and military members, and moderate opposition leaders and fighters. The transitional governing body would then be created.

In May, the Syrian parliament would dissolve, according to the timeline. The Security Council would recognize the new transitional authority and lay out the transition’s next steps. These include major political reforms, the nomination of an interim legislature and an international donors’ conference to fund Syria’s transition and reconstruction.

The next six months, through November 2016 — when Obama’s successor is elected — would be devoted to the sides drafting a new constitution. The Syrian people would get a chance to vote on that document in a popular referendum in January 2017, according to the timeline.

Only then would the process lead to the end of Assad’s rule of Syria.

In March 2017, the timeline reads: “Asad relinquishes presidency; inner circle departs.” (The document uses the U.S. government’s preferred spelling of Assad.)

Syria’s new government would assume full powers from the transitional body after the parliamentary and presidential elections in August.