The Army chief of staff said Thursday he’s worried that a $6 billion combat communications system that has been under development for the past decade might not work, prompting frustration from senators.

Gen. Mark Milley told the Senate he will likely finish a “rigorous, thorough and painful” review in six weeks of the system, called the Warfighter Information Network-Tactical, to determine whether it can provide secure communications to soldiers in war zones as intended.