The Pentagon said Tuesday that it is "regrettable" that China pulled out of the China-US Cyber Working Group in response to the US indictment of five Chinese military officials for cyber espionage. "That's regrettable. But it's a decision they made. And that's a regrettable decision. Wasn't a decision they had to make," Pentagon Press Secretary John Kirby told reporters. But, He added, "this is a tough issue we don't always agree on, but it's one that we got to keep the dialogue and the conversations open on," saying Defense Secretary Chuck Hagel "firmly believes in still doing that." He affirmed "we still desire, from a military perspective, to further grow and develop the military-to-military relationship and to find ways to have a more productive conversation about these very tough issues, and cyber is one of them." He reiterated "we have no desire to militarize cyberspace, and with countries like China who are active in cyber, we want to continue to have as open and as transparent a conversation about it as possible." He affirmed that "this is a relationship that is important to us. It matters." He noted that there are "plenty of issues that we disagree on. And it's fair to say, and it's certainly clear in the indictment of what this military unit was responsible for, that cyber is one of those issues that we don't see eye-to-eye on in every aspect, all the more reason to keep the military-to-military communications open and keep working at this." Kirby stressed that cyber is a "difficult issue, and it's an issue that we do have differences with the Chinese over, as evidenced in this indictment." Five Chinese military hackers were indicted on Monday for "computer hacking, economic espionage and other offenses directed at six American victims in the US nuclear power, metals and solar products industries." The Chinese government summoned US Ambassador to China Max Baucus and has also decided to suspend activities of the China-US Cyber Working Group