Iran summoned the Swiss envoy representing U.S. interests in Tehran on Sunday to protest against President Donald Trump saying Washington would target Iranian sites if Tehran attacks Americans or U.S. assets in retaliation to the killing of military commander Qassem Soleimani.

Trump said on Saturday the United States has targeted 52 Iranian sites that it would strike if Iran attacks Americans or U.S. assets in response to a U.S. drone strike that killed Soleimani in Iraq. Trump’s tweet said that those targets would include sites “ important to Iran & the Iranian culture,” which drew quick condemnation from domestic critics.

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The Pentagon declined to comment on the 52 targets and referred questions to the White House, which did not respond.

Read more: The four critical questions after the assassination of Iran's Soleimani ■ To avert war with Iran, Trump will need all the strong nerves and sophistication he sorely lacks ■ Overseas Black Ops units await Iran's signal to strike ■ Iran's 'crushing revenge' may prove formidable challenge for Soleimani's successor ■ By assassinating Soleimani, U.S. takes another step towards war with Iran

Tehran has vowed "crushing revenge" for the killing, saying that the assassination will double motivation to retaliate against the U.S. and Israel.

Iran’s Supreme National Security Council said it has reached a decision on how to respond to the attack, but isn’t saying what the decision is.

Open gallery view Participants wave placards during a protest against recent United States military actions in Iraq January 4, 2020, outside the state Capitol in downtown Denver. Credit: AP/David Zalubowski

The council's brief statement after a special session Friday said it investigated “the different aspects of this incident and it is announcing that the United States of America is responsible for all consequences of this criminal adventure.”

Trump wrote in a series of tweets that Iran "is talking very boldly about targeting certain USA assets" to avenge Soleimani's death. Trump said the United States has "targeted 52 Iranian sites" and that some were "at a very high level & important to Iran & the Iranian culture, and those targets, and Iran itself, WILL BE HIT VERY FAST AND VERY HARD."

"The USA wants no more threats!" Trump said, adding that the 52 targets represented the 52 Americans who were held hostage in Iran after being seized at the U.S. embassy in Tehran in 1979.