Responding to growing concern among war-weary constituents about the purpose and cost of the U.S. mission in Libya, senators are poised to debate whether to send President Barack Obama a message that he needs to be more specific about his goals there.

Obama defended his policy Tuesday during a joint news conference in Washington with German Chancellor Angela Merkel.

„Chancellor Merkel and I share the belief that (Libyan leader Moammar) Gadhafi needs to step down for the sake of his own people,“ Obama said.