Washington (CNN) -- A preliminary U.S. Navy plan to allow its chaplains to perform same-sex marriages in military chapels after the end of "don't ask, don't tell" has fired up congressional opposition.

All services are moving forward with the transition from the present ban on gays and lesbians serving openly in uniform. Top Pentagon officials are expected to sign off on the new rules and the progress of training in coming weeks.

An April 13 memo from the Navy officer in charge of chaplains says they "may" officiate at same-sex marriages or civil unions, depending on both local laws and their religious organization.

It is not clear if the other services would have a similar provision.

"Regarding the use of base facilities for same-sex marriages, legal counsel has concluded that, generally speaking, base facility use is sexual orientation-neutral," Rear Adm. Mark Tidd, the Navy's chief of chaplains, said in the memo. "This is a change to previous training that stated same-sex marriages are not authorized on federal property."

After the pending rule change was reported in the Navy Times and Stars and Stripes newspapers, it drew criticism from dozens of members of Congress.

A letter from Rep. Todd Akin, R-Missouri, to the secretary of the Navy asking him to block the change has been signed by 63 members of Congress, according to Akin's website.

Akin says the Navy's permission for gay weddings in military chapels, once the current policy formally is ended, would violate the federal Defense of Marriage Act.

"While a state may legalize same-sex marriage, federal property and federal employees, like Navy chaplains, should not be used to perform marriages that are not recognized by federal law," Akin said on his website. "My colleagues and I are calling on the secretary of the Navy to make sure that the Navy actually follows the law. As we state in the letter, 'It is not the place of any citizen of this country to pick and choose which laws they are going to obey. We expect citizens sworn to defend those laws to set the example in their application.'"

The Pentagon said in a statement Monday that the Defense of Marriage Act "does not limit the type of religious ceremonies a chaplain may perform in a chapel on a military installation." However, while the Defense of Marriage Act still stands, the Defense Department would not recognize those unions as valid marriages even if they're performed in a state that recognizes same-sex marriages.

Cmdr. Danny Hernandez, the Navy's assistant chief of information, told CNN that under the same-sex marriage proposal, each chaplain would be bound by his own religious beliefs. "A chaplain can conduct a same-sex ceremony if it is in the tenets of his faith," Hernandez said.

And he said the policy would have no impact on military benefits. When Defense Secretary Robert Gates and others announced that the Pentagon would end the "don't ask, don't tell" policy, they made it clear that benefits for spouses and survivors are a complicated issue that would require more study and planning.