Events Sunday concerning Syria, as US Secretary of State John Kerry presses a diplomatic offensive in Europe to justify military strikes against the Damascus regime over an alleged chemical attack.

President Bashar al-Assad's regime is accused of using chemical weapons in an attack on August 21 that killed hundreds of people near Damascus.

- Kerry meets Arab League ministers in Paris, and says they had agreed that the Assad regime had crossed a "global red line" with the alleged attack on August 21.

"All of us agree, not one dissenter, that Assad's deplorable use of chemical weapons... crosses an international global red line," Kerry says.

He adds that a number of Arab countries are willing to sign a statement agreed by 12 countries of the G20 that called for a reaction to the alleged attack.

- Assad has denied he was behind the chemical attack and calls on American lawmakers to reject planned US military strikes, warning of possible retaliation, CBS television says.

- White House Chief of Staff Denis McDonough tells CNN the Obama administration is already planning "for every contingency" in case of any fallout from US military strikes against Syria.

- British Foreign Secretary William Hague tells the BBC: "I do believe very strongly that the world must stand up against the use of chemical weapons. The risks of not doing so in my view are greater than the risks of doing so."

- The Pentagon is readying more intense and longer attacks on Syria than originally planned, set to last three days, the Los Angeles Times reports.

- Iranian Foreign Minister Mohammad Javed Zarif says in Baghdad that any US-led airstrikes against Syria would be "illegal" under the UN Charter.

- Syrian rebels, including jihadists linked to Al-Qaeda, are reported to have taken control of the historic Christian town of Maalula north of Damascus as they try to tighten their grip around the capital.

- Assad ally Moscow says a Russian plane has landed in the Syrian port city of Latakia, as it seeks to evacuate its citizens from the escalating conflict.

- Pope Francis lashes out at what he termed "commercial war to sell arms" as he leads mass prayers in Saint Peter's Square for Syria.

- Israel deploys a battery of its Iron Dome missile defence system near Jerusalem as Prime Minister Benjamin Netanyahu calls Israel "an island of tranquillity, quiet and security" amidst "the storm raging around us".