President Donald Trump's tweets are White House statements and should be carefully considered, former diplomat Richard Haass told CNBC on Wednesday.
"The president would be wise to put down his phone or only to do it after the potential tweets have been reviewed the same way that any White House statement would be," Haass, the president of the Council on Foreign Relations said on "Power Lunch."
He believes Trump is a "neophyte when it comes to foreign policy."
The president, who has a habit of tweeting about various issues, took to Twitter earlier Wednesday to warn Russia to "get ready" for a potential U.S. strike against Syria. Moscow has backed the Syrian government during the country's seven-year civil war.
In response, Haass tweeted that national security issues are "much too serious and dangerous" to conduct on Twitter.
Haass told CNBC that Trump's "confrontational rhetoric" toward Russia and China ought to give people pause, whether he means what he says or not. If he doesn't mean it, "people start to discount what he has to say."
"Either way I don't think he's doing himself or his country any good by his use of his cellphone," said Haass, who was a principal advisor to former Secretary of State Colin Powell from 2001 to 2003. He also was a special assistant to former President George H.W. Bush and served in the State Department during the Reagan administration.
Haass' comments echoed those of Nicholas Burns, former U.S. ambassador to NATO, who told CNBC earlier Wednesday that "this is not a video game."
"The president of the United States needs to be calm and needs to act presidential," said Burns, who has advised Republican and Democratic presidents and is now a professor at Harvard's Kennedy School of Government. "The tweet this morning was irresponsible. And it wasn't presidential. It wasn't effective."
The Kremlin responded to Trump's tweet by saying it did not engage in "Twitter diplomacy."
Trump's threat came after the Russian ambassador to Lebanon said his nation's military would intercept American missiles and potentially target the U.S. craft that fired them. The potential American strike follows a suspected chemical attack on the rebel-held city of Douma, allegedly by forces loyal to Syrian President Bashar Assad.
Haass said Trump's response has raised expectations. He expects the president to use force against Syria, but thinks it will likely be more of a "spasm, a punitive attack."
"It won't change the fundamentals," he said. "Bashar Assad will still be in power. If he wants to use chemical weapons a month from now he'll still have the capability to do that."
If Trump really wants to make a difference in Syria, it's less about "shooting off a couple of missiles" and is more about the long-term American plans for the country, said Haass, author of "A World in Disarray."
However, he wouldn't rule out the likelihood of U.S. forces remaining in Syria for the "foreseeable future."
Meanwhile, the Middle East turmoil isn't the only thing Haass is concerned about.
"I've run out of fingers to count the things that worry me these days," he said. That includes the trade situation, U.S. debt, North Korea, and a U.S. economy that has been "overjuiced" by tax cuts and spending increases.
"There's more sources of instability at work now."
The White House did not immediately respond to a request for comment.
— CNBC's Tom DiChristopher and Reuters contributed to this report.