WASHINGTON (Nexstar) — This week, senators got the chance to grill top U.S. Department of Homeland Security officials on how they plan to handle the expected surge of migrants once Title 42 is lifted on May 23.

Title 42 is the public health policy that allows U.S. Customs and Border Protection to turn away migrants at the southern border over concerns of COVID-19.

But senators said they’re concerned that the administration’s plan won’t be ready by the end of May.

“We are already surging personnel, resources, transportation resources to the border,” said DHS Secretary Alejandro Mayorkas.

Senators, including Kyrsten Sinema, D-Arizona, said they are not convinced the administration’s six-pillar plan is enough.

“As of this moment, I do not feel confident that the system is ready for this mass migration,” Sinema said.

DHS predicts up to 18,000 migrants will try to cross the southern border each day if Title 42 is revoked.

“The Border Patrol tells us that they believe that they will lose, as they say, operational control,” said U.S. Sen. Rob Portman, R-Ohio.

Portman said Title 42 wasn’t expected to be permanent, but lifting it too soon is dangerous.

“It’s not meant to be an immigration law, but it is all we have right now to keep the system from being totally overwhelmed,” Portman said.

U.S. Sen. Maggie Hassan, D-New Hampshire, said plans aren’t always enough.

“It isn’t clear that having the plan and actually having the resources on the ground to meet the goals of that plan are the same thing,” Hassan said.

Senior administration officials remain confident they are ready, telling lawmakers every border sector has different needs.

“Whether it’s additional federal law enforcement personnel, contract civilian processors to free up border patrol agents,” said DHS Senior Coordinating Official MaryAnn Tierney.