The U.S. has advised Americans in 14 countries in the Middle East to leave, issuing a warning two days after the war began.
Both the House and the Senate have prepared war powers resolutions for votes this week.
Roughly 3,000 federal officers are currently deployed in the state.
Denmark, Norway, Sweden, France, Germany, the United Kingdom, the Netherlands and Finland would face the tariff.
Trump's comments came hours before Vice President JD Vance was to host Danish and Greenlandic officials for talks.
President Trump did not offer any details about what the help would entail.
Presidents Trump and Putin are holding a press conference following their meeting in Alaska to discuss ending the Russia-Ukraine war.
U.S. Immigration and Customs Enforcement's Reno sub-office has deported a Mexican who was convicted of murder.
Australia had an exemption from such tariffs during Trump’s first administration.
President Trump plans to cover a range of issues in his meeting with Japanese Prime Minister Shigeru Ishiba.