As planners look to redesign the Freedom Tower, citing security concerns lodged by the New York Police Department, Commissioner Raymond Kelly said yesterday that developers have known about unresolved police questions about security at the former site of the World Trade Center for more than 16 months.

In a statement issued late yesterday afternoon, Mr. Kelly rebutted assertions in recent press reports that the development team did not know about the security concerns until April 8, when the department issued its most recent security assessment to developers.

“Some of our critics have little insight into this thorough and necessary process,” Mr. Kelly said in the statement.

Last November, The New York Sun outlined the Police Department’s trouble with the designs for the Freedom Tower. The department, which conducts site and terrorism assessments for proposed buildings around the city, have maintained that current plans for the tower place the building too close to the street.

Without a buffer zone to properly “harden the target,” police officials have said, the new tower could be at high risk from a truck bomb or car bomb.

Looking to satisfy the department’s security concerns, the lead developer of the World Trade Center site, Larry Silverstein, has proposed acquiring public financing to revise the location of the Freedom Tower – a shift in planning that could delay the beginning of construction by up to a year.

Development officials have also recently criticized the Police Department for raising the costly concerns late in the development process.

“I don’t want to say the police have been irresponsible, but where were they until this month?” the chairman of the Lower Manhattan Development Corporation, John Whitehead, said, according to a front-page article in yesterday’s New York Times.

“I wish they had called attention to the seriousness of the problems earlier, rather than at this late stage,” Mr. Whitehead was quoted was saying.

More than six months ago, however, a member of Mr. Whitehead’s board, Madelyn Wils, told the Sun that the Police Department had already expressed concerns about the designs.

The commissioner said the questions have been raised “since the end of 2003.” That, Mr. Kelly said, is when his department first “focused attention on security issues concerning the Freedom Tower through a series of meetings” and “correspondences” with developers.

“The Freedom Tower is going to be an iconic building on an incredibly complicated site,” Mr. Kelly said. “It is critical that we get the security absolutely right.”

Mr. Whitehead and other development officials could not be reached for comment yesterday.