In a wide-ranging with Fox News' Brian Kilmeade, former CIA Director David Petraeus praised President Trump's hard line on NATO, claimed the west needs to rethink its North Korea strategy and warned the United States should be "firm, not provocative" with China.

The retired four-star general said Trump is hardly the first U.S. president to take NATO to task for spending too little on their own defense and depending on the U.S. to make up the difference.

"(Trump) is right to do that," Petraeus said. "He is by no means the first president. I heard President Obama do this publicly and privately. I heard Secretary Gates, President Bush, others... have all been very frustrated that our NATO allies have not spent what they have agreed to spend."

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He added, "The greatest gift to nato since out end of the Cold War is Vladimir Putin. He has given a whole new reason for NATO to live."

When it comes to North Korea, the former head of US Central Command said the west needs a more realistic approach in dealing with Pyongyang's nuclear ambitions.

"The real question is do we truly believe that we can demand that North Korea agree to complete irreversible, verifiable destruction of their nuclear program before we do anything? Or is -- should we do a step-by-step starting out with a on the ground verification inspection, validation of what is there? The secretary of state (Mike Pompeo) is a seriously bright guy. We do have dialogue. I think he understands..

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Petraeus then shifted to China and the challenges facing the Trump administration. He believes both countries have to "compete" and "collaborate" in order to be successful.

"We should look at every decision that we take and ask what will the effect of that be on our relationship with China? What we need to be here is firm not provocative," Petraeus said. "We want to ensure that China realizes that if there are actions that they take that are not acceptable to us, that there is going to be a response."

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On Friday, the U.S. escalated its trade war with China, slapping tariffs on $200 billion worth of Chinese exports after trade talks held in D.C. failed Thursday.

Beijing hit back and pledged to take "necessary countermeasures" though it did not give specifics.

Brian Kilmeade's full interview with former CIA Director David Petraeus will be available this weekend.