With only two days before the U.S.- and Russia-planned ceasefire in Syria, Russian officials said Thursday there were no alternatives to the agreement. “We’ve already said everything on the ‘plan B’ — there never was one, and there never will be,” said Russian Foreign Minister Sergey Lavrov, Russian news agency Tass reported.

The remarks come after U.S. Secretary of State John Kerry said Tuesday he could not vouch for the success of the ceasefire but argued it was the best way forward for peace while also mentioning the possibility of a plan B that could involve the partition of Syria.

“It may be too late to keep it as a whole Syria if we wait much longer,” Kerry told the U.S. Senate foreign relations committee Tuesday, underscoring that he would move in the direction of a partition if the ceasefire does not work.

Russian President Vladimir Putin spoke with Syrian President Bashar Assad Wednesday, inserting himself in the center of political action, and suggesting the U.S.-Russia ceasefire could stand a chance of lasting. Part of the agreement includes allowing humanitarian aid to reach dangerous and besieged areas.

“The main goal is to stop the bloodletting in Syria,” said Russian presidential spokesman Dmitry Peskov, indicating that Moscow was focused on plan A and was not considering a backup plan.

Many elements of the ceasefire remain unclear, with the Syrian opposition group known as the High Negotiations Committee warily eyeing the agreement, saying they feared Russian and Syrian government forces would continue bombing and attacks, the Associated Press reported. Ahead of the ceasefire, Russia has doubled the number of its attack helicopters in an effort to aid Syrian government troops fighting the Islamic State group, economy and weapons analysis group IHS Jane’s reported.

“The Americans are taking note of our concerns, and we are waiting for their replies,” said the group’s spokesman, Salem Al Meslet.

American officials remain hesitant working with the Kremlin, with one unnamed source describing the ceasefire as having “not a whole lot of meat on that bone,” the Washington Post reported. The almost five-year civil war in Syria has taken the lives of more than 250,000 people and displaced millions. The U.S.-Russian ceasefire is set to begin Friday at midnight local time.