The threat of blowbacks from Iran could continue for years and may come in the form of covert or diplomatic action, an expert said on Wednesday.

Jarrett Blanc, a senior fellow at the Carnegie Endowment for International Peace, warned of a "further, overt response" if U.S. President Donald Trump "gloats" in a statement he is set to make on Wednesday morning stateside.

Following a U.S. airstrike that killed Tehran's top commander Qasem Soleimani last week, Tehran fired more than a dozen ballistic missiles at bases housing American troops in Iraq early Wednesday morning local time.

Iranian Foreign Minister Mohammad Javad Zarif said on Twitter that Iran "took & concluded proportionate measures in self-defense."

But Blanc told CNBC's "Capital Connection" that this is unlikely to be the end of Iran's vowed retaliation.

"I think it is almost inconceivable that this is the end of Iran's reaction," he said. "It might be the end of Iran's short-term reaction, it might be the end of Iran's overt reactions, but I think that there will continue to be blowbacks from Iran from the Soleimani assassination, whether that's covert action or certainly diplomatic action over the mid to long term," Blanc said.

There's a "huge number" of directions that Iran can take, Blanc said. "They can certainly have their own assassination attempt. There could be a covert or terrorist attacks against U.S. interests in the region or elsewhere."

He added that Tehran could continue to push the Iraqi government to force U.S. troops out of the country, though a "final decision" has not been made.