President Donald Trump is not the only one with the flexibility to make a last-minute decision during Saturday's G-20 trade meeting, a former official in the administration of George W. Bush told CNBC on Friday.

Bilateral meetings at the G-20 summits "really are quite structured," said Robert Kimmitt, a former deputy Treasury secretary and former U.S. ambassador to Germany. Yet, Chinese President Xi Jinping "is powerful enough in their system that he could come in with a very well prepared, very well structured agenda. But depending what he hears from the president, he too could call an audible."

Wall Street has been hoping that Trump and XI will keep the trade war between the U.S. and China from escalating. The two countries are locked in a conflict that's seen each side imposing tariffs on each other's products. In the latest moves, the U.S. levied 10 percent duties on $200 billion worth of goods from China, prompting Beijing to put tariffs on $60 billion worth of U.S. goods.

Before departing for the summit in Buenos Aires, Argentina, on Thursday, Trump told reporters that the U.S. is "close to doing something with China but I don't know that I want to do it." On Tuesday, the president told The Wall Street Journal that it's "highly unlikely" that he would delay the tariff hike on those $200 billion worth of Chinese goods from 10 percent to 25 percent. He even reiterated his threat to put tariffs on the rest of Chinese imports.

Kimmitt, who has decades of experience in both the government and private sector, said in a "Squawk Box" interview that it appears Trump tends to make quick decisions "at the last moment," but said there is a small chance a breakthrough deal is worked out during the meeting. Kimmitt also said China will have to meet the U.S. halfway on alleged unfair practices such as intellectual property theft.