NEW YORK -- Calling Penn Station the "single most critical transit hub in the United States," NYPD Commissioner Ray Kelly voiced frustration that basic security measures there still are not in place.

In a letter to various warring parties that have not implemented needed security improvements, Kelly urged immediate talks so a security barrier can be placed around the station. In his March 25 letter obtained by WNBC.com, Kelly wrote, "This impasse has gone on for too long."

Kelly's frustration was directed at the owners of Madison Square Garden, the chairman of Vornado Realty Trust, the head of the MTA and the president of Amtrak. Kelly did praise the MTA for securing millions of dollars to build the permanent security perimeter, a perimeter that would be complete with bollards and delta barriers able to stop truck bombs.

Currently, the streets between West 31st and 34th streets between 7th and 8th avenues either have no barricades or are surrounded with dirt-filled planters.

Paul DeMatteis of John Jay College said many of the planters would do little to stop a vehicle bomb from hitting Madison Square Garden or Penn Station.

"These things they have laid out here are totally ineffective," DeMatteis said. "We don't want someone to look at this building and say, 'It's easy.' But right now, it's easy."

A spokesman for the MTA said three years ago the agency secured $15 million to help put in a permanent security barrier. But "Madison Square Garden has refused to accommodate the security plan and we cannot proceed with this important project without their permission and cooperation," said spokesman Jeremy Soffin.

A spokesman for James Dolan, MSG's chairman, said the Garden is working with the NYPD, Amtrak and Vornado Realty trust to come up with a solution.

Some of the infighting appears to be centered on which properties the security perimeter will be placed and who will pay for the manned checkpoints.

A spokesman for Amtrak and Vornado Realty's Steven Roth declined comment.

Hundreds of thousands of people pass through Penn Station each day. In his letter, Kelly said, "The only near-term option for improving the protection of this complex is a sound security perimeter."

Rep. Peter King, R-Long Island, called the delays "unacceptable." King called for the private owners and public agencies to come up with an immediate agreement. "It's essential for all the parties to get this resolved as quickly as possible," King said.

A spokesman for Kelly said he has no comment on what was supposed to be a private letter. Kelly did warn "there simply is no evidence that the terror threat is in any way diminishing."

There was no word from any of the parties on when they might meet again to try to hammer out a deal.

New York State Homeland Security Director Michael Balboni responded to the story late Tuesday by issuing a statement: "We join in Commissioner Kelly's concerns and support the MTA's efforts to increase security at all transit facilities."