U.N. Secretary General Ban Ki-moon on Wednesday urged the international community to delay military action against Syria and focus on diplomacy, but Britain said it was preparing a draft resolution authorizing “all necessary measures” to protect Syrian civilians after last week’s alleged chemical attack.

The resolution, which a spokesman for Prime Minister David Cameron said would be presented later Wednesday to the five permanent members of the U.N. Security Council, is seen as a precursor to possible military strikes by Western powers.

It is likely to face resistance from Russia, which has steadfastly backed the government of Syrian President Bashar al-Assad, including in the wake of the attack on at least three rebel strongholds that left hundreds of men, women and children dead and many others injured.

“Britain has drafted a resolution condemning the attack by the Assad regime, and authorizing all necessary measures under Chapter 7 of the U.N. Charter to protect civilians from chemical weapons,” Cameron announced on Twitter. “The resolution will be put forward at a meeting of the five permanent members of the Security Council later today in New York.”

The decision to go to the United Nations signaled the desire by Britain and other Western powers to build a stronger legal case for military action, even as top U.S. officials said intelligence agencies have convincing proof that Assad’s government bears responsibility for the attack.

Timeline: Major events in Syria’s tumultuous uprising that began in March 2011.

“We have always made clear that we want the U.N. Security Council to live up to its responsibilities on Syria,” a spokesman for Cameron said. “Today we are giving its permanent members the opportunity to do that.”

Ban, speaking in The Hague, said the Security Council should not be “missing in action” as the world weighs its reaction to Syria’s worsening civil war. “Give peace a chance. Give diplomacy a chance,” Ban said, according to the Associated Press. “Stop acting and start talking.”

Cameron is recalling Britain’s Parliament for a debate on Syria on Thursday, with a rash of lawmakers, including many from his Conservative Party, calling for clear evidence of culpability by Assad’s government and concrete assurances that military action would be limited and would produce an outcome in the best national interests of Britain and other Western powers.

The prime minister, who spoke by phone Tuesday night with President Obama, has encountered significant domestic calls for caution. The archbishop of Canterbury, Justin Welby, warned in the Daily Telegraph on Wednesday against a rush to judgment.

“You do something in one area and it has an impact far away, in a most serious way,” said Welby, who visited the Middle East in June and has spoken to people there extensively in recent weeks.

“The overwhelming sense is of a really moving and terrible sense of fear about what might come out of, what might be happening in the next few weeks,” Welby told the London newspaper. “A sense that this a terribly, terribly dangerous time.”

In Syria, U.N. chemical weapons experts restarted investigations into the alleged toxic gas attack, after a day’s hiatus due to security concerns.

Residents cheered “God is great” as a convoy of white SUVs marked with the U.N. logo passed through the town of Meliha under rebel protection, videos posted online showed.

Activists said the team later arrived in Zamalka, a town in the suburban agricultural belt known as the Eastern Ghouta, where rockets carrying poisonous gas allegedly fell last week, killing scores of residents.

The investigations are focused on determining whether chemical weapons were used, not who deployed them.

Loveday Morris in Beirut contributed to this report.