Protesters hold up a damaged U.S. flag and anti-USA banners during a demonstration following the U.S. airstrike in Iraq which killed a top Iranian commander, in Tehran, Iran, on Friday, Jan. 3, 2020.

The U.S.-China trade fight dominated investors' attention for much of 2019 — but that will likely get overshadowed by tensions between the U.S. and Iran this year, a political risk consultant predicted Monday.

"I actually think this (Iran) is going to be a more important issue for investors this year than China-U.S.," Alastair Newton, director of Alavan Business Advisory and a former British diplomat, told CNBC's "Squawk Box Asia."

He predicted more Iranian retaliation this year, after Tehran fired missiles at Iraqi bases housing U.S. troops last week in retaliation for the U.S. killing of top Iranian general Qasem Soleimani.

Newton didn't predict how Iran could retaliate, but other experts have said future moves could include aggression by Iranian proxy groups in the region and cyberattacks.

Newton said the relationship between the U.S. and Iran is "just going from bad to worse," and there have been no signs the two sides could turn to diplomacy to resolve their conflict. His comment came as President Donald Trump tweeted that he "couldn't care less" if Iran agrees to negotiate.

Trump on Twitter: National Security Adviser suggested today that sanctions & protests have Iran "choked off", will force them to negotiate. Actually, I couldn't care less if they negotiate. Will be totally up to them but, no nuclear weapons and "don't kill your protesters."

Tehran wouldn't want to negotiate with Trump either, Newton said.

Iranian authorities "are not going to talk with Donald Trump, the Iranians will hope that Donald Trump is defeated" in this year's U.S. presidential election and they have a Democratic Party administration to deal with, he said.