U.S. President Barack Obama warned Syrian leader Bashar Assad on Monday not to make the "tragic mistake" of turning to his stockpile of chemical weapons.

Assad's beleaguered regime had earlier threatened to unleash the weapons if Syria faced international military intervention, although it vowed not to turn them against its own civilians.

There were tears for the victims, and cheers for those who prevented even more lives being lost, as the Colorado town of Aurora stood silent Sunday to grieve the Batman theater massacre.

Some 3,000 mourners gathered three blocks from the multiplex where James Holmes allegedly opened fire on those attending a packed midnight screening of "The Dark Knight Rises" on Friday, killing 12 and injuring 58.

The families of three U.S. citizens killed in drone strikes in Yemen last year -- including al-Qaida preacher Anwar al-Awlaqi -- have filed a civil lawsuit against top U.S. officials.

The family members argue that the U.S. government's killing of the three men "violated fundamental rights afforded to all U.S. citizens, including the right not to be deprived of life without due process of law."

U.S. defense officials have held talks with their Israeli counterparts over whether Israel might strike at Syria's weapons facilities as its regime faces possible collapse, the New York Times reported.

The Times on Wednesday cited officials as saying that the Pentagon is not advocating military action because it feels that such an attack would help Syrian President Bashar Assad rally support against foreign intervention.

Forsaking his annual vacation in Martha's Vineyard to campaign for re-election, U.S. President Barack Obama has admitted to a bit of holiday blues as his daughters head off to summer camp.

Obama said he was going to spend most of the summer campaigning ahead of the November 6 election and to make matters worse his daughters Malia, 14, and Sasha, 11, were soon going to be flying the White House nest.

A U.S. federal judge sentenced an Uzbek man to more than 15 years in prison Friday on terror and weapons charges for threatening to kill U.S. President Barack Obama, U.S. prosecutors said.

Ulugbek Kodirov, 22, was sentenced to 15 years and eight months in prison for providing material support to terrorism, threatening to kill the president and possession of a firearm by an illegal alien, they said in a statement.

U.S. President Barack Obama authorized the use of $10 million in emergency funds on Thursday for people displaced by the conflict in northern Mali, the White House adding it was "deeply concerned".

The funds will support efforts of the United Nations High Commissioner for Refugees, White House National Security Council spokesman Tommy Vietor said.

Crossroads GPS has purchased a $25 million ad blitz in nine battleground states to attack President Barack Obama's record on jobs and the debt, the advocacy group supporting Republican Mitt Romney said Friday.

The wave of advertisements, which roll out on July 10 and run through early August, begins with a spot called "Excuses," which focuses on the disappointing report released Friday that shows poorer-than-expected U.S. jobs growth and a stagnant unemployment rate of 8.2 percent.

The United States has moved new forces into the Gulf to keep strategic waterways open and strike deep within Iran in the event of a regional military escalation, the New York Times reported Tuesday.

The Times cited senior officials as saying the quiet build-up was aimed at reassuring Israel that Washington is serious about addressing Iran's nuclear program and keeping the Straits of Hormuz -- a key oil choke point -- open.

A U.S. drone attack on a militant compound in Pakistan's northwestern tribal area killed six insurgents on Sunday, security officials said.

The unmanned aircraft fired two missiles on the compound in Shawal district, 50 kilometers (30 miles) southwest of Miranshah, the main town of North Waziristan tribal district, near the Afghan border, they said.