WASHINGTON, April 2: The United States may cross an invisible red line if it keeps sending more soldiers from the army and Marine Corps to Iraq and Afghanistan, warns chairman of the US Joint Chiefs of Staff Admiral Mike Mullen.

The US Army and Marine Cops have sent tens of thousands of service members to operations in Iraq and Afghanistan and Admiral Mullen believes that seeking more sacrifices from them will place too much strain on the force.

The top US military official also warned that the spike of violence in Basra and southern Baghdad shows that “there are tough days ahead in Iraq.”

He stressed the need for creating a balance between mission demands and lengthy and repetitive deployments to lessen the strain on the forces.

Admiral Mullen said he is convinced that the US Army has to get deployments down from 15 months to 12 “as fast as possible.”

The army also must increase “dwell time” -- the time soldiers spend at home following deployments, he said.

“We’ve been (deploying soldiers at an increased rate) since 2003 … and repetitive deployments are really taking a strain,” he said.