NEW YORK — As officials prepare seven alternative plans for reconstruction of the World Trade Center — including a memorial in the sky and the world’s tallest tower — doubts about who is in charge of the process threaten to muffle the fanfare.

“Things are very unclear,” said Mark Ginsberg, a leader of New York New Visions, a coalition of architects and planners. “There are all these different agencies coming out with different plans — hopefully with some coordination.”

The Lower Manhattan Development Corp., a city-state agency created after last year’s terrorist attacks to guide downtown redevelopment, plans to unveil seven new designs Dec. 18. Several of the plans include a tower that would be the tallest in the world, said a redevelopment official who spoke on condition of anonymity. Malaysia’s Petronas Twin Towers, at 1,483 feet, are now the world’s tallest.

All of the plans include memorials to the victims of the Sept. 11 attack, the official said. One plan places it on top of a building, while another incorporates a formal, sunken garden.

“They’re inspiring. I think they are exactly what we need,” said Roland Betts, a board member of the development agency who has seen early versions of the plans.

But as the plans near public release, the Port Authority of New York and New Jersey, which owns the 16-acre trade center site, says it expects to produce a separate master plan early next year.

The development corporation released its first batch of six proposals for the trade center last July. The plans all featured office buildings grouped around a memorial to the Sept. 11 victims — and all were dismissed as bland and boring.

The agency then put out a call for new architects to produce designs with relaxed requirements for the amount of commercial space the new buildings must accommodate.

A final plan is to be chosen in February.

The development corporation and the Port Authority have promised several times to cooperate, only to have their efforts later diverge.

Port Authority Executive Director Joseph Seymour said last month that his agency’s plan for ground zero would focus on nuts-and-bolts concerns such as transportation improvements.

Appearing to contradict Seymour, development corporation head Louis Tomson said last week that the authority’s architect would not release his own plan but would work with the development corporation’s staff “to review the plans that are presented by the seven architects.”

Tomson acknowledged “many spirited debates” between the two agencies but said they are working together. How the two agencies’ plans will be merged is unclear, although an official familiar with the rebuilding process said Sunday the agencies reached an agreement last week on a single integrated master plan process.

Some independent urban planners worry that government agencies won’t produce a design worthy of the challenge. Robert Yaro, president of the Regional Plan Association, said he recently joined a group of civic leaders touring comparable projects in Europe such as Berlin’s Pottsdammer Platz.

“Everywhere we went, business leaders, government leaders said that there are very, very high expectations for what we’re going to deliver at the trade center site,” he said. “The world is watching.”