A Yemeni soldier looks at protesters who hold a rally outside the U.S. embassy in Sanaa against drone strikes in Yemen, on April 29, 2013. Yemeni activists staged a rally on Monday to denounce U.S. drone strikes in Yemen. The U.S. has stepped up drone attacks against al-Qaeda militants in Yemen's southern regions this year which killed dozens of civilians and sparked mass protests. (Xinhua/Mohammed Mohammed) 

Yemeni protesters hold banners that shows civilians killed by U.S. drones during a rally outside the U.S. embassy in Sanaa against drone strikes in Yemen, on April 29, 2013. Yemeni activists staged a rally on Monday to denounce U.S. drone strikes in Yemen. The U.S. has stepped up drone attacks against al-Qaeda militants in Yemen's southern regions this year which killed dozens of civilians and sparked mass protests. (Xinhua/Mohammed Mohammed) 

A Yemeni protester holds a banner that shows civilians killed by U.S. drones during a rally outside the U.S. embassy in Sanaa against drone strikes in Yemen, on April 29, 2013. Yemeni activists staged a rally on Monday to denounce U.S. drone strikes in Yemen. The U.S. has stepped up drone attacks against al-Qaeda militants in Yemen's southern regions this year which killed dozens of civilians and sparked mass protests. (Xinhua/Mohammed Mohammed) 

A Yemeni protester holds a banner "Drones are the weapons cowards" during a rally outside the U.S. embassy in Sanaa against drone strikes in Yemen, on April 29, 2013. Yemeni activists staged a rally on Monday to denounce U.S. drone strikes in Yemen. The U.S. has stepped up drone attacks against al-Qaeda militants in Yemen's southern regions this year which killed dozens of civilians and sparked mass protests. (Xinhua/Mohammed Mohammed)