What presidents normally do is work with their team to develop a policy that reflects the United States' allies, military generals and military analysis of how statements will impact the situation, she explained.
"Here you have a situation where the president is just clearly just making it up as he goes along and trying some bellicose language because he thinks that will work," Soderberg said in an interview with "Power Lunch."
Earlier this week, Trump said if North Korea made any more threats to the U.S., it will be met with "fire and fury." North Korea responded by saying it was considering a plan to attack Guam and dismissed Trump's warnings as a "load of nonsense." On Thursday, Trump said his previous statement may not have been tough enough.
"Force has always been an option, but it has always been the last option, not the first," Soderberg said. "Rather than let that take effect and squeeze the North Koreans and get them back from the brink, we're escalating it and using language that President Kim uses in North Korea. That's not who we are."
And that doesn't mean talk hasn't been tough — the U.S. has been speaking forcefully to North Korea all this time, said Ellen Tauscher, former U.S. under secretary of state for arms control and international security under President Barack Obama.
"We just didn't do it in public," she said. For one, they didn't want to put somebody in a corner.
"This is not an ideal situation. We have a rogue dictator in the hermit kingdom who is starving his people, selling them as slaves, trading in contraband, trading in arms, under U.N. sanction without any real influence by the United States or the West," Tauscher told "Power Lunch."
On Thursday, Defense Secretary James Mattis said the military is ready to counter the threat from North Korea, but also said the effort is being "diplomatically led."
— CNBC's Terri Cullen, Jacob Pramuk and John Shinal contributed to this report.
Watch: North Korea rhetoric ramps up