Stock markets tumbled Monday morning after President Donald Trump threatened to more than double tariffs on China in a tweet Sunday.

Trump tweeted he would levy a 25 percent tariff on imported goods from China, an abrupt and unexpected increase amid ongoing trade talks.

Charles Sennott, who heads up The GroundTruth Project and is a news analyst with WGBH News, told Boston Public Radio Monday that Trump's tweets destabilize a conversation that was otherwise progressing.

"Yes, he's done some great work on trying to bring China forward on trade agreements that would be more favorable to America, and yes, this thing seems to have pretty decent motion, and yes hopefully the talks will stay on track," he said. "But why ... do you do this tweet and really rock the markets, really create instability and questions around what is going to happen with China?"

Immediately after Trump tweeted about China on Sunday, Dow Jones Industrial Average futures dropped more than 500 points.

The president reinforced his message Monday, tweeting, "The United States has been losing, for many years, 600 to 800 Billion Dollars a year on Trade. With China we lose 500 Billion Dollars. Sorry, we're not going to be doing that anymore."

Sennott said Trump's actions are affecting everyday people in America, citing his own sticker shock when he went to purchase a new dishwashing machine.

"The global economy shapes our lives, and the way Trump has addressed this, and the way the economy is doing, well — it does really well for some people, it doesn't do well for many," he said. "Anyone, all of us, whether you're in the middle class, upper middle class, or you're struggling, this is impacting us, too."

Sennott also touched on other international headlines, such as ratcheted up violence between Israel and Palestinians in Gaza and unrest in Venezuela.