Al Qaeda's branches in the Gulf and North Africa have issued a rare joint statement calling on warring militants in Iraq and Syria to join forces against the United States. "We call upon [the Muslim community] to support our people in Iraq and Sham and support them with the valuable and priceless, and stand in their ranks against ... America, the source of evil and symbol of corruption and injustice," said the statement, posted Tuesday to an official Twitter account. It is thought to be the first statement to be issued by both al Qaeda in the Arabian Peninsula (AQAP) and al Qaeda in the Islamic Magreb (AQIM).

In addition to trying to topple the government of Syrian President Bashir Assad, al Qaeda offshoot ISIS has battled several rival Islamist rebel groups including Nusra Front, al Qaeda's wing in the country. ISIS forces have also taken over swathes of Syria's neighbor Iraq, prompting more than 100 U.S. air strikes. On Monday, Secretary of State John Kerry joined leaders from more than 20 countries at a strategy meeting in Paris.

IN-DEPTH

- F. Brinley Bruton

Reuters contributed to this report.