Defense Secretary James Mattis told the US Army it “must stand ready” and have military options that “our president can deploy” in case diplomacy fails to solve the standoff with increasingly belligerent North Korea.

“There’s one thing the US Army can do, and that is you have got to be ready to ensure that we have military options that our president can employ if needed,” Mattis told the Association of the US Army’s annual meeting in Washington, DC, on Monday, according to The Hill. “But that means the US Army must stand ready, and so, if you’re ready, that’s your duty at this point in time. And I know the Army will always do its duty.”

Addressing Secretary of State Rex Tillerson’s effort to reach out to Pyongyang and United Nations sanctions against President Kim Jong Un’s rogue regime, Mattis said US military readiness can act as a deterrent.

“What we want to do is be so ready and be very much aware that we fight the way we come, that everybody in the world wants to deal with Secretary Tillerson and the Department of State, not the Department of Defense and the United States Army,” the former Marine Corps general said.

He also said the Pentagon should make Congress aware of the military situation “in compelling and persuasive terms.”

“There are times when those of us who wear the uniform can be rightly condemned for being overly conservative, wanting more insurance and more boats and planes and guns and tanks and I understand that,” Mattis said. “But I think the more we can explain we have the time right now to prepare for war is the best way to prevent war, should conflict break out, to get money later, will not be good enough because we won’t have the time at this point.”

​The defense secretary’s comments come as President Trump in tweets over the weekend and on Monday bemoaned diplomatic efforts by previous presidential administrations that tried to curtail North Korea’s weapons programs.

“Our country has been unsuccessfully dealing with North Korea for 25 years, giving billions of dollars & getting nothing. Policy didn’t work!,” Trump tweeted on Monday.

In the past two months, Kim’s government has successfully test-fired intercontinental ballistic missiles capable of striking the US mainland and detonated a nuclear device.