A senior American officer involved in training Iraq’s new security forces is warning against putting too much responsibility on those forces too quickly, as pressure grows in the United States for the start of a withdrawal of U.S. troops.

A video has been released showing kidnapped British Gaza-based journalist Alan Johnston in an apparent suicide bomber explosives belt and warning it will be detonated if an attempt is made to free him by force.

A suicide bomber killed six Iraqi tribal leaders opposed to al Qaeda when he blew himself up at a busy Baghdad hotel, in one of four attacks on Monday that killed 50 people in all, police said.