One of the more conspicuous missing links in the nearly completed Pittsburgh-to-Washington, D.C., bike trail will start to materialize on Monday.

Construction will begin on a 2,017-foot bike and pedestrian promenade at the Monongahela Wharf, Downtown. It is the first of three phases that ultimately will connect Point State Park with trails to Oakland, the South Side and points far beyond.

Some parking spaces will be lost starting Monday, but "this is for the betterment of the city and the waterfront," said Anthony Boule of the Pittsburgh Parking Authority.

Those who can't find a space at the wharf will be urged to try the First Avenue Garage (an $8.75 all-day rate, 75 cents more than the wharf). There they can pick up a free ride into Downtown on the T.

Eventually 150 to 200 of the wharf's 700 spots will be taken by the trail, said Kelly Rabenstein, communications manager for the Riverlife Task Force, which is overseeing the $2.3 million project.

The promenade will extend the entire length of the wharf along the river's edge.

Two other pieces will be needed to connect the Point and wharf to the Eliza Furnace Trail from Downtown to Oakland.

Longer-range plans call for a 1,400-foot concrete path on steel pilings that will curve out over the Monongahela River around the Fort Pitt Bridge piers and link the park and the wharf. At the other end, a switchback ramp will lift cyclists from the wharf to the Smithfield Street Bridge.

Projected completion dates for those phases were not available yesterday.

The other missing links in a continuous 335-mile path to the nation's capital are about four miles of a 9-mile stretch from near Sandcastle Waterpark in West Homestead to McKeesport.

The Regional Trail Corp. is negotiating to place bridges over Norfolk Southern Railway tracks in Whitaker and Duquesne, project coordinator Jack Paulik said yesterday, and the talks are going well.

Linda McKenna Boxx, president of the Allegheny Trail Alliance, said the group needs to raise about $1.5 million to complete the missing pieces. She said she hoped the McKeesport-to-Sandcastle section could be completed by the end of next year's cycling season.

Sandcastle is a separate obstacle. The park owners have balked at allowing the trail through their property, an 0.7-mile stretch that might be the last and most confounding link to be completed.

Allegheny County Executive Dan Onorato and Kennywood/Sandcastle President Peter J. McAneny in October announced they had made significant progress toward accommodating the trail on Sandcastle property.

Mr. McAneny has since resigned. County officials hope to resume the talks with the new park leadership in the coming month, said Kevin Evanto, Mr. Onorato's spokesman.