President Barack Obama has ordered a cutoff in U.S. imports of charcoal from Somalia, hoping to starve the militant Islamist group al-Shabab of resources.

The step is one of several in an executive order Obama issued Friday targeting Al-Shabab, whose attacks have helped keep Somalia without a fully functioning government for more than two decades. Other measures include freezing the assets of individuals accused of threatening the peace in Somalia, obstructing humanitarian efforts and attacking African Union peacekeeping forces.

Obama's order says charcoal exports "generate significant revenue" for al-Shabab militants.

In a letter to Congress, Obama says the steps aim to combat corruption, piracy and a deteriorating security situation in the east African country.