Updated

Republicans are turning up the heat on the Obama administration in a bid to scramble his plan to close the Guantanamo Bay detention center and relocate its prisoners by January 2010.

Sen. Saxby Chambliss, R-Ga., planned to hold a press conference Wednesday to discuss his bill to block funding for the release of any Guantanamo prisoners into the United States.

Sen. Jeff Sessions, R-Ala., circulated a stinging letter this week that he wrote to Attorney General Eric Holder in which he questioned what "legal authority" the administration has to admit dangerous detainees into the U.S.

And Senate GOP Conference Chairman Lamar Alexander, R-Tenn., stirred up Republican opposition with a new Web video dedicated to discrediting Obama's proposal to close the prison. The video, set to the foreboding music of "Carmina Burana," mixes clips of accused terrorists' photographs with news broadcasts about the release of Guantanamo prisoners and road signs from the various states where lawmakers warn the terrorists will be sent.

It ends with the message: "Terrorists. Coming soon to a neighborhood near you. January 2010."

Republicans appear to be building off House Democrats' move this week to leave out money for closing Guantanamo in a war funding bill. They are increasingly raising flags about the danger the transfer of prisoners could pose if they are released in the U.S.

In his letter to Holder, Sessions requested assurances that "dangerous detainees" will not be allowed into the U.S. civilian population. He cited U.S. law that prohibits the admission of militants trained at terrorist camps into the United States, and said it would be "reckless and hypocritical" for the administration to violate that law.

He also criticized Holder for reports that he joked about putting detainees in hotels (when asked a question about doing so) during his recent trip to Europe, where he tried to convince European nations to admit some detainees.

"I clearly do not share your sense of humor on this matter," Sessions wrote. "It would be both dangerous and contrary to our immigration laws to admit trained foreign militants into our civilian population."

Senate Republican Leader Mitch McConnell of Kentucky has been hammering the White House and congressional Democrats for weeks on the matter, saying Tuesday that the prisoners are "some of the most hardened terrorists in the world."

But Sen. Tom Harkin, D-Iowa, said Tuesday he thinks the administration still has the support of enough lawmakers to save the money for closing Guantanamo. He said he doesn't understand the fears that prisoners will pose a threat to the U.S. population.

"They can't go anywhere," Harkin said. "You put them in security. ... They're in jail."

Iowa does not have a maximum security federal facility, but Harkin said he wouldn't mind prisoners being sent to Iowa "if we had a big federal prison."

Guantanamo currently houses 240 detainees, about 60 of whom were identified by the Bush administration as being unable to be returned to their countries of origin because of fears they will be tortured or executed.

Holder announced last month that 30 detainees have been cleared for release or transfer, up from 17. He did not indicate whether they will be set free or put in prison. So far, France has formally agreed to take in a single detainee as a symbolic gesture; many other countries have signaled their unwillingness to assist. Some other countries have been amenable.

But several countries in Europe are reluctant to take the prisoners, partly because of the security risk and partly because of the cost.

House Minority Leader John Boehner told FOX News on Wednesday that even if U.S. allies agree to admit more detainees, he'd be concerned about whether the U.S. can have confidence that they will continue to be detained.

Republican Sens. John McCain of Arizona and Lindsey Graham of South Carolina raised several questions about the planned Guantanamo closure in an Op-Ed in Wednesday's Wall Street Journal. They questioned what the administration would do with detainees who cannot be tried but are too dangerous to release, how it would prosecute detainees suspected of war crimes without military commissions and how the administration can prevent released detainees from returning to fight against the U.S.

They said enemy combatants should not be tried in civilian courts and that the idea that combatants have to be tried or released "is a false choice."

FOX News' Trish Turner contributed to this report.