Rockefeller (D-W.Va.) said that he is asking his colleagues in the Senate “to join him in a letter to President Obama discouraging the administration from cutting Medicaid coverage for the nation’s most vulnerable citizens, including low-income children, parents, pregnant women, people with disabilities and senior citizens.”

A Rockefeller aide said the senator doesn’t know what the president will propose in his speech on Wednesday and the statement was to “push back against Republican plans to cut the program.”

Rep. Paul Ryan has proposed block-granting the program and cuts of $771 billion over 10 years.

A White House spokesman deferred on answering questions about Rockefeller’s statement, pointing to a comment by Jay Carney, the president’s press secretary, made during a briefing Tuesday:

Where the president believes the House Republican plan fails starkly, is that it is imbalanced; it places all the burden on the middle class, on seniors, on the disabled, on people in nursing homes, through its rather drastic reform of Medicare and Medicaid — reform which in many ways is an elimination of the established entitlements that they represent. So that’s not the approach the president believes is the right way to go.

Democrats are expected to receive a briefing on the speech early Wednesday, but so far, no details of the proposal have leaked.

A long-time advocate for Medicaid patients, who now lobbies on their behalf, praised Rockefeller for challenging the White House.

“I am very glad to see Jay Rockefeller stand up, slap his shoe on the table and say ‘hell no’ to deep Medicaid cuts,” Licy Do Canto, who formed the Partnership for Medicaid, said. The “unease” about what Obama is planning is widely held in the Medicaid community, he said, and what eventually will be proposed is anyone’s guess.

Not knowing what the president is planning, Do Canto said, “is giving Democrats like Rockefeller and others a great amount of agita.”

Vicki Gottlich, a senior attorney with the Medicare Rights Center, said “obviously, we are quite pleased to see Sen. Rockefeller standing up for people with low incomes.”

This article first appeared on POLITICO Pro at 5:43 a.m. on April 13, 2011.