The Trump administration is threatening to halt some travel from four countries refusing to cooperate with the Department of Homeland Security on deportations.

DHS officials confirmed to Fox News that letters have been sent to the State Department seeking the suspension of visas for some of those countries' citizens.

A State Department official explained to Fox News that "when we receive such notification, the Department of State works to implement a visa suspension as expeditiously as possible in the manner the secretary determines most appropriate under the circumstances to achieve the desired goal."

Government officials refuse to specify the countries that will be affected. But the dispute centers on countries refusing to accept nationals who have been deported or delaying their return.

It's also unclear who exactly could be affected by a visa suspension.

“The secretary [of State] is having conversations with those countries. We want to bring those countries into compliance. We want those countries to be able to take back their citizens," a State Department official said. "We are having different levels of conversations with those countries and imposing different things upon them based on what we think will work best with those countries.”

Fox News’ Nick Kalman contributed to this report.