Saudi Arabia's foreign minister urged on Tuesday the international community to have a unified position over Syria after the war-torn country's opposition formed a coalition last month.

"We see in forming the new Syrian coalition an important positive step towards uniting the opposition under one banner," Prince Saud al-Faisal told reporters.

Germany warned Syria Tuesday against any use of chemical weapons, ahead of a NATO meeting on Turkey's request for deployment of Patriot missiles to counter a potential threat from its neighbor.

"I can only warn the Syrian regime: a use of chemical weapons would be totally unacceptable," German Foreign Minister Guido Westerwelle said ahead of the gathering of his NATO counterparts in Brussels.

A Tunisian suspected of involvement in an attack on the U.S. consulate in Benghazi in which the U.S. ambassador to Libya was killed is refusing to be interrogated by FBI agents, his lawyer told Agence France Presse.

"They wanted to interrogate him as a witness, but he has refused," Abdelbasset Ben Mbarek said late on Monday, referring to his client Ali Hamzi, and denouncing what he called "interference" in the Tunisian judicial system.

Syrian rebel fighters on Monday shot down a MiG warplane in Damascus province that had been bombing rebel strongholds, activists said.

Details of the incident were scarce and there was no immediate confirmation from the Syrian authorities.

Israel had no reason to oppose Palestine's U.N. observer state membership, according to ex-prime minister Ehud Olmert, who plans to announce Wednesday whether he will run in the next polls.

"I have made my decision and I will announce it in two days," Olmert told Agence France Presse of his political future, after a speech in New York late Monday during which he renewed criticism of Prime Minister Benjamin Netanyahu's handling of the Israeli-Palestinian conflict.

Australia Tuesday joined Britain and France in summoning the Israeli ambassador to convey its "grave concern" over plans to build new settlements in east Jerusalem and the West Bank.

Foreign Minister Bob Carr said the Israeli proposal, and plans to withhold tax revenue from the Palestinian Authority, "enormously complicate the prospects for resuming negotiations between the two sides.”

President Barack Obama dramatically told Syria's President Bashar Assad Monday not to turn chemical weapons on his own people, following U.S. warnings his forces were mixing deadly sarin gas.

Obama publicly told the increasingly isolated Assad not to unleash the "worst weapons of the 20th century" in the 21st, capping a day of alarming American warnings on the Syrian regime's intentions.

Syria has begun mixing chemicals that can be used to make deadly sarin gas, a U.S. official told AFP Monday, amid fears that President Bashar Assad's forces could attack rebels with chemical weapons.

"We've picked up several indications which lead us to believe that they're combining chemical precursors," the official said, on condition of anonymity, adding that the operation was apparently aimed at making sarin.

The European Union has decided to reduce its Syrian delegation because of security fears, the spokesman for the bloc's diplomatic chief said Monday, amid new fears chemical weapons could be used in the ongoing conflict.

"The EU delegation has decided to reduce activities in Damascus to a minimum level due to the current security conditions," spokesman Michael Mann said in a statement, after the United Nations announced it was indefinitely suspending operations in Syria and withdrawing non-essential staff.

Israel has revived a plan to construct 1,600 new settler homes in the east Jerusalem neighborhood of Ramat Shlomo that raised U.S. objections when it was first announced in 2010, an official said on Monday.

"In the next two weeks the interior ministry's district committee for Jerusalem will convene to discuss the objections to the program that was approved for deposit over two years ago," interior ministry spokeswoman Efrat Orbach told AFP.