The Maryland Transit Administration's proposed Red Line in Baltimore has received U.S. approval to move to the next phase of development, a strong indication that the east-west light rail line will eventually qualify for federal funding.

Gov. Martin O'Malley plans to announce Tuesday that the Federal Transit Administration has given the state the green light to move into what is known as preliminary engineering, or PE — a phase that would take the project beyond the conceptual stage and into specific planning.

The approval would start a roughly two-year planning process for the 141/2-mile line fromWoodlawn to Bayview — a project that the federal agency estimated would cost a total of $2.2 billion with inflation. The state previously described the Red Line as a $1.8 billion project in 2010 dollars.

The decision does not mean the federal government has agreed to pay for the project's construction. Henry Kay, the MTA's deputy administrator for planning, said that decision would be made later. But he said the federal action means the Red Line has survived a process that weeds out many projects.

"It's a big deal," Kay said. "PE approval really represents a major milestone."

But opponents of the project questioned the importance of the federal action.

"The reality of this is that there's no money," said Benjamin Rosenberg, a resident of Canton. "The likelihood of the funding in the next couple years is zero."

Kay said the PE process will cost about $65 million. He said that many of the engineering contracts have been awarded and that work has been awaiting federal approval. He said the state would likely pay most of the upfront costs but would be eligible for federal reimbursement when money becomes available.

While the Red Line has the enthusiastic support of the O'Malley administration, Mayor Stephanie Rawlings-Blake and most city elected officials, it faces opposition from some residents of neighborhoods in its path — especially those in Canton and West Baltimore.

Plans for the Red Line call for the tracks to run in one long tunnel under downtown and Fells Point and in one shorter tunnel under Cooks Lane in West Baltimore. The rest of the route would run above ground, including sections on Boston Street and Edmondson Avenue.

Advocates contend the Red Line is needed to relieve traffic congestion and to provide an attractive transit alternative to reach some of the city's major employment centers, including the Inner Harbor, Harbor East, the University of Maryland professional schools and the Johns Hopkins Bayview Medical Center.

"Baltimore has been underserved by public transit," said Sen. Benjamin L. Cardin. "We are now closer to having a truly integrated, regional transit system that will help transform our city and our region, adding a convenient, affordable east-west alternative to the ever-increasing gridlock."

But opponents maintain that a light rail line would detract from the ambience of the neighborhoods it runs through and would fail to attract the ridership officials have projected.

In fact, while they gave the Red Line the OK to move to the next step, federal officials may have also given opponents ammunition by lowering the estimates of daily ridership from 60,000 to 57,000 and hanging a higher price tag on the project.

Kay said it's not unusual for ridership estimates to fluctuate during the planning of a transit line. And he noted that the agency approved the move to the next step despite the lower ridership figures.

"When they signed off on 57,000 they agreed we're making reasonable assumptions," he said.

The new, $2.2 billion figure represents a difference in the way the federal agency computes costs and the way the state does, Kay said.

"It's not because the price has gone up or we've changed the scope" of the project, he said.

Nevertheless, the federal estimate would also raise the amount of money the state would have to come up with to pay its likely 50 percent share of the project.