The Trump administration's get-tough approach to Iran, including an executive order putting a halt to travelers and immigrants coming from that country along with six other Muslim-majority nations, has Democratic critics even more worried about the fate of American citizens and others with strong U.S. ties imprisoned in Iran.

In the last remaining weeks of the Obama administration, a cadre of White House officials had reportedly hoped they could secure one last deal with Iran and bring home at least some of the five hostages with strong U.S. ties being held there.

But hopes started fading for the hostages' release after Trump's executive order. Tehran responded in kind, putting a stop to any U.S. citizens traveling to Iran for the foreseeable future.

What's more, in the wake of an Iranian missile test, the administration imposed new tariffs on Teheran. And this week, Trump's national security adviser Michael Flynn put "Iran on notice" that the U.S. would no longer tolerate violations of international agreements.

Maryland Sen. Ben Cardin, the ranking Democrat on the Foreign Relations panel, told the Washington Examiner that Trump's immigration ban and more bellicose language on Iran has broad implications for U.S. allies and could also prevent the safe return of Americans or permanent legal U.S. residents held in Iran.

"It affects America's credibility globally, including our ability to speak out for individuals who are in stress situations, such as those who are being held hostage to be able to get the appropriate attention or to be able to get people moving back and forth the way they should," he said.

The White House says the travel ban is necessary in order to put a stop to potential terrorists entering the United States while the administration devises a new vetting system.

An Iranian with an interest in securing hostages' release may want to travel to the United States to speak to U.S. officials about it.

"That person is now barred from coming to the United States," Cardin said. "It's dangerous because of individuals who could be trapped in countries and may never survive as a result of this. It's dangerous because Americans may be a greater target than they are today. It's dangerous because of recruitment by terrorist organizations that are using this."

The bottom line, he said, is the ban "makes us much less safe, and there are people who are going to get hurt."

There are at least five dual-Iranian citizens or people with western ties that the Islamic Revolutionary Guard Corps has imprisoned in the wake of the signing of the nuclear deal between Iran, the Obama administration, and other world powers.

Siamak Namazi, an Iranian-American businessman; his father, Baquer Namazi; Nizar Zakka, a Lebanese citizen and permanent legal resident of the United States; Kamran Ghaderi, an Iranian-Austrian dual citizen; and Alireza Omidvar, an Iranian-American businessman are being held. Iran has repeatedly said it has no information on Robert Levinson, an American private investigator and former FBI agent who disappeared in Iran in 2007.

A controversial prisoner swap in January 2016 between Iran and the U.S. freed four Iranian-Americans, including Washington Post journalist Jason Rezian. But the other hostages were either left behind or imprisoned after that prisoner exchange.

Many hawkish Republicans on Capitol Hill wary of the Obama administration's Iran nuclear deal have praised Trump's new sanctions on Tehran even as they criticized his immigration ban as lacking proper vetting, especially when it comes to Iraqi interpreters for the military and diplomats seeking refuge in the U.S.

After the administration announced new sanctions against Iranian individuals, Graham called them a "first step in a long journey to check the Ayatollah and his radical regime."

Graham said he didn't think Trump's travel ban would have "any impact" on the ability to negotiate a deal with Tehran to release the hostages.

"Iran is using these people as they used people in the past as pawns in a bigger game so you can't let these six hostages situation stop what would be a reasonable position, which is better vetting" of travelers and immigrants to the U.S., he told the Washington Examiner.

"It's in our national security interest to change the dynamics in the Middle East," he said. "And we can't let a country grab hostages and let it change our foreign policy."

Sen. Ron Johnson, R-Wisc., who sits on the Foreign Relations Committee, agreed.

That Iran imprisoned more dual citizens in the wake of the Iran deal, "just shows what an awful agreement it was."

"It didn't modify Iran's behavior to the better – it modified it to the worse – it emboldened them," he told the said in a brief interview. "So our response has to be to fully enforce the Iranian agreement, and that means slapping on additional sanctions. And we have to stick to the overarching goal to prevent Iran from becoming even more of a menace."

"We always want prisoners, hostages back – but what overrides all of that is what is in the best national interest in securing peace and security," he added.