U.S. President Barack Obama is warning Syria against using chemical weapons, saying that would be a "tragic mistake."
Obama told a veterans convention in the western city of Reno, Nevada Monday that the world is watching Syria. He said President Bashar al-Assad would be held accountable if his nation used poison gas and other deadly chemicals.
A Syrian Foreign Ministry spokesman, Jihad Makdissi, said the government would never use chemical weapons against its own people, but would unleash them against what he called foreign invaders. He said the military is securely guarding the nation's weapons stockpile.
Israeli Prime Minister Benjamin Netanyahu said Sunday he is deeply concerned about what would happen to Syria's stockpile if the Assad government collapses. He said the Israeli army is preparing to act if Syrian weapons fall into the hands of Hezbollah or other Islamic militants.
Fighting between between rebels and government troops continued Monday in the capital, Damascus, and the northern city of Aleppo as the European Union tightened sanctions against Syria.
The European Union has tightened the noose on Syria's government, strengthening an arms embargo, blacklisting nearly 30 people and companies associated with the regime, and banning the Syrian national airline from landing in EU countries.
With the conflict intensifying in Syria, EU foreign ministers moved on two fronts: strengthening sanctions against the regime of President Bashar al-Assad and freeing up more humanitarian assistance for Syrians fleeing the violence.
During talks in Brussels, they added more than two dozen names of Syrian people and companies that face EU travel bans and asset freezes. Most of the individuals are military officials.
Syria's national carrier is also banned from landing in EU airports, although it can fly over European countries and make emergency stops.
The ministers also tightened a 2011 EU arms embargo against the Syrian regime. Member states are now required to search suspect planes and ships. Until now, the searches were optional.
And with a flood of Syrians now fleeing their country, the ministers agreed to earmark another $24 million in aid to Syrian refugees, to an overall total of $76 million. But British Foreign Secretary William Hague says more needs to be done.
"We have to step up our humanitarian assistance for the people fleeing across the borders, to give more practical support to the Syria opposition, including helping them prepare for Syria after Assad, and to encourage other countries outside [the] EU to impose serious and effective sanctions on the Assad regime which we are making some progress in doing," Hague said.
The ministers also discussed possibilities for a post-Assad Syria.
French Foreign Minister Laurent Fabius said the EU is looking at how to assemble a post-Assad transitional government that will represent all of Syria's diverse population.
Thousands of Syrians have died and tens of thousands have been uprooted since an anti-government uprising began more than a year ago.
Meanwhile, Arab League foreign ministers indicated during a meeting in Qatar Monday, that they hoped Mr. Assad would step down, saving the Syrian people any further suffering.
Qatari Foreign Minister Sheikh Hamad ben Jassem ben Jabbar al Thani said that the league was offering President Assad the possibility to leave Syria with his family without threat of prosecution.
But the Syrian Foreign Ministry spokesman said that the matter of who governs Syria is "a matter for the Syrian people to decide." He said the Arab League was "aggravating the situation" inside the country.
Lisa Bryant from Paris and Edward Yeranian from Cairo contributed to this report.