World powers agreed on the conditions of a ceasefire in Syria on Friday but did not see hostilities ending for another week, giving the regime time to continue its siege of Aleppo, the last rebel stronghold in the north.

Troops loyal to President Bashar Assad, including Russian bombers and Shia militias from Lebanon and Iran, are on the verge of seizing the last opposition-held neighborhoods of what was once the largest city in the country.

Russian airstrikes, which started in September, have already enabled Assad to reclaim territory east of his Alawite homeland on the Syrian coast, squeezing the relatively moderate rebellion that is supported by the Arab states and Turkey in between the regime on the one hand and the self-declared Islamic State militant group on the other.

No one is shooting back

Adam Garfinkle, a Middle East policy expert, is cynical of the promise to stop the fighting.

“It is easy to cease firing when no one is shooting back because they are mainly dead,” he writes for the Foreign Policy Research Institute.

Assad’s forces earlier retook Homs, one of the first cities that rose up against him in 2011.

Between 250,000 and 470,000 civilians are believed to have been killed since the conflict began nearly five years ago. Millions of Syrians have been displaced.

Islamists excluded

American secretary of state John Kerry and Russian foreign minister Sergei Lavrov announced the deal after talks in Munich, Germany.

The agreement does not compel Russia to stop its airstrikes. Lavrov told reporters the truce does not apply to militants of the Islamic State and the Nusra Front, two fanatical Islamist groups that descended from Al Qaeda.

“Our airspace forces will continue working against these organizations,” he said.

But by far most Russian airstrikes have targeted other insurgent groups that more directly threatened Assad’s government.

The Munich agreement falls short of a formal ceasefire since it was not signed by the main warring parties.