Grand Rapids, Mich. ? President Bush ran into GOP and Democratic resistance to his Medicare reform proposal Wednesday, with even White House allies saying they were confused about what the president intended to propose and a key Republican pledging to block the plan.

Bush flew more than 1,000 miles round-trip to highlight a top domestic priority: revamping Medicare to give beneficiaries prescription drug subsidies.

“A reformed and strengthened Medicare system, plus a healthy dosage of Medicare spending in the budget, will make us say firmly, ‘We fulfilled our promise to the seniors of America,”‘ Bush said.

He offered no details, but even as he spoke, on Capitol Hill there was growing criticism of Bush’s proposal.

Democrats and some consumer groups contended the plan would deny the elderly the doctors of their choice by forcing them into HMOs if they wanted prescription drug coverage.

“His proposal is really a benefit for HMOs,” said Rep. Nancy Pelosi, D-Calif.

Even some Republicans weren’t enthusiastic, with Sen. Olympia Snowe, R-Maine, saying the “president’s focus on ways to reform Medicare could hamper our efforts to pass comprehensive prescription coverage.”

Bush, meanwhile, tried to showcase the softer side of his domestic and international agenda, promoting new AIDS money and Medicare changes while visiting a state vital to his re-election.

But there was widespread confusion — even among key Republicans — over his Medicare plan.

President Bush, speaking a day after his State of the Union address, takes his Medicare reform message to Grand Rapids, Mich. Confusion abounded Wednesday about the Bush plan, details of which have not been settled.

“We’re not even close to understanding what the president is going to propose,” House Majority Leader Tom DeLay, R-Texas, said on Capitol Hill.

Administration officials have said in recent days that the plan would offer the drug benefit to seniors willing to leave the traditional fee-for-service program and join government-subsidized health care plans administered by insurance companies. But on Wednesday, officials were noncommittal about whether the administration would take that route.

Republican Sen. Chuck Grassley of Iowa, chairman of the Senate Finance Committee — which has jurisdiction over Medicare reform — indicated Wednesday he would not support a plan that limited prescription drug coverage to those who agree to leave traditional fee-for-service Medicare.

“We need to strengthen Medicare, first by adding prescription drug coverage that’s available for all seniors, not just those that switch into managed care,” Grassley said. “All of our changes should be voluntary. If you like what you have now, you should be able to keep it. That means I won’t draw lines on drug coverage, regardless of the choice they make.”

Perhaps reflecting some of the criticism, Bush aides said Wednesday it could be weeks before specifics are rolled out. Spokesman Ari Fleischer said the administration was still finalizing key elements of the plan.

White House officials seemed caught off guard by the criticism and by the barrage of questions they faced from reporters pressing for details when the administration had made Medicare Bush’s central issue of the day.

One senior official said Wednesday night that the White House was just starting its consultations with lawmakers and that it planned in the “near future” to send the broad outline of Bush’s goals to Congress.

During his Michigan appearance, Bush renewed his pledge to seek $400 billion over 10 years to change Medicare, mostly to pay for the prescription drug benefit.