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.