The Silver Spring Transit Center, shown on March 20, is four years late in its expected delivery and $50 million over budget because of design and construction issues. (Sarah L. Voisin/The Washington Post)

Metro has told Montgomery County officials that some of the recent repairs to the Silver Spring Transit Center are showing “signs of degradation,” and it is asking the county for $15 million to cover future maintenance and repair.

County officials, in turn, accuse Metro of attempting to hold “hostage” the delivery of the problem-plagued facility to the transit agency until its demands are met.

The new round of charge-and-countercharge is the latest in a long history of interagency discord surrounding the three-level commuter hub, which is four years late and $50 million over budget because of design and construction issues.

Under the terms of a 2008 agreement, the Washington Metropolitan Area Transit Authority is to take control of the building upon completion. Metro would operate the center, which is adjacent to its Silver Spring station, as a part of its regional bus and train system.

County officials said this month that repairs are virtually complete. They also said they had been working with Metro operations and marketing staff toward an Aug. 9 handoff of the facility, followed by an Aug. 23 opening.

Metro officials said Monday that no such certain date had been contemplated and that any final acceptance of the transit center into the bus and rail system would require action by the Metro board.

On July 21, the county received from Metro proposed amendments to the 2008 agreement. It said that the county’s repairs, which added about $21 million to the facility’s estimated $140 million price tag, did not address all of the concerns outlined in a 2013 engineering report.

“Some of the remediation repairs are showing signs of degradation already,” a preamble to the amendments said, although there was no specific mention of what the problems are. The Metro document added that the transit center “already is cracking at an abnormal rate due to construction and design deficiencies.”

Metro asked the county to place $15 million in escrow to cover “extraordinary maintenance and repair” of the facility in the future. It also asked that the county relinquish to Metro its 25 percent interest in any future development on land adjacent to the transit center (the agency has the other 75 percent) and a 100 percent tax abatement for 10 years on any development at the site.

In a letter to Metro’s interim general manager, Jack Requa, on Monday, the county’s chief administrative officer, Timothy Firestine, called Metro’s requests “preposterous.”

“I am troubled that at this late hour WMATA appears to be holding transfer of the facility hostage until the County accedes to unreasonable demands,” he wrote.

In an interview Monday evening, Firestine said he believed the transit agency, hurting for cash, was angling for a last-minute advantage.

“They think they are in a position where they can negotiate,” Firestine said, adding that it was the county’s intention to turn the building over to Metro in the coming days, without further condition.

While Metro was threatening not to take delivery of the facility, it was also running its buses through the building on Monday for driver training purposes.

In a statement late Monday evening, Metro spokeswoman Sherri Ly said the agency was “surprised” by the county’s position that the outstanding issues “are anything less than legitimate and substantive.”

Ly said Metro officials have been waiting for more than two weeks for the county to set up a meeting so that the remaining issues can be addressed.