WASHINGTON — The United Nations Security Council on Saturday unanimously called for a 30-day cease-fire in Syria, with Russia agreeing to the temporary hiatus only after forcing two days of delays that critics said allowed ally Syrian President Bashar al-Assad to pursue a renewed bombing campaign.

Bombings have been blamed for hundreds of recent deaths in a rebel-controlled area.

A new wave of airstrikes and shelling on eastern suburbs of Damascus, the Syrian capital, left at least 22 people dead and dozens wounded Saturday, the Associated Press reported. That raised the civilian death toll from a week of bombing in the area to more than 500.

Under the UN resolution, the nationwide truce will begin ‘‘without delay,’’ a victory for the United States and other nations that resisted Russian efforts to push back the start or soften the terms.

It came after intense negotiations to persuade Russia not to use its veto power in the Security Council. Moscow had blocked 11 previous Syria resolutions.

The United States and others accused Moscow of protecting the Assad government and its bombing campaign in the Damascus suburb of Eastern Ghouta while allowing a horrific humanitarian disaster to continue.

There was a further delay Saturday as Russia and the United States haggled behind closed doors over the final text. Cameras in the Security Council chamber captured other delegates poring over the document shortly before the session finally began, more than two hours behind schedule.

Nikki Haley, the US ambassador to the UN, said little had changed during the arduous negotiations, ‘‘except a few words and some commas.’’ She blamed Russia, Syria, and Iran for not taking moral responsibility for the urgency of the situation.

‘‘As they dragged out the negotiation, the bombs from Assad’s fighter jets continued to fall,’’ she said. ‘‘In the three days it took us to adopt this resolution, how many mothers lost their kids to the bombing and shelling? How many more images did we need to see of fathers holding their dead children?

‘‘All for nothing, because here we are voting for a cease-fire that could have saved lives days ago.’’

It will be up to Russia to use its influence with Assad to enforce the cease-fire, which would allow desperately needed deliveries of emergency supplies and medical evacuations of the seriously injured and sick.

Activists and monitors said more than 500 civilians have been killed in the last week in Eastern Ghouta, in what is considered the fiercest assault in seven years of civil war. Each day of delay in imposing the cease-fire allowed Assad’s forces to level more of the largely rebel-controlled area.

The humanitarian convoys ‘‘are ready to go,’’ Swedish Ambassador Olof Skoog told the council.

‘‘This ended up being a bit of a showdown,’’ between Haley and Russian Ambassador Vasilly Nebenzia, said a Security Council diplomat who requested anonymity to describe the backroom negotiations.

‘‘She succeeded in retaining vital language in the resolution that called for an immediate start to the cease-fire and unfettered humanitarian access without delay. The Russians kept trying to water it down.’’

On Friday, a vote was scheduled, and delayed, three times before diplomats gave up the effort after sundown.

One sticking point was when the cease-fire would begin. The draft submitted Friday night by Kuwait and Sweden did not give a specific start time.

It would demand ‘‘that all parties cease hostilities without delay for at least 30 consecutive days throughout Syria for a durable humanitarian pause, to enable the immediate delivery of humanitarian aid and services and medical evacuations of the critically sick and wounded.’’

The resolution would encourage efforts toward a longer cease-fire but does not set terms for that goal. It also would carve out an exception for military action against the Islamic State, Al Qaeda, and other terrorist groups.

Some diplomats suspect Russia was stalling a vote to allow government warplanes to press on its offensive against rebels with missiles, mortars, and barrel bombs.

Hospitals also have been hit, and the pleas coming from some of the 400,000 residents of the area have grown increasingly desperate in the face of what UN officials describe as a medieval siege. UN Secretary General António Guterres labeled conditions in Eastern Ghouta ‘‘hell on earth.’’

World leaders appealed to Russia to back a truce allowing a temporary reprieve to the unrelenting bombardment.

President Trump accused the Syrian government and its backers, Russia and Iran, of being responsible for a humanitarian ‘‘disgrace.’’

French President Emmanuel Macron and German Chancellor Angela Merkel appealed in a joint letter to Russian President Vladimir Putin to back a cease-fire.

Haley supported the cease-fire idea and, in remarks Thursday, criticized Russia for ‘‘trying to give cover’’ to its ally Assad.

She said US military strikes like those Trump ordered a year ago are ‘‘always going to be on the table,’’ and said Russia had walked away from its previous cooperation in the removal of chemical weapons from Syria.

‘‘Russia has covered for Assad many times we now have to decide what’s the response to that,’’ Haley said during a question-and-answer session at the University of Chicago’s Institute of Politics.