WASHINGTON >> The Secret Service has been forced to relocate its Trump Tower command center to a trailer outside the midtown skyscraper in New York after a lease agreement between the General Services Administration and the Trump Organization fell apart last month, two people with knowledge of the negotiations said today.

The Secret Service has had a presence in Trump Tower since late 2015, when then-candidate Donald Trump became a front-runner in the race for the Republican presidential nomination. For much of that time, it ran its operations from space inside the building, just one floor below Trump’s triplex residence.

The GSA, which arranges real estate transactions on behalf of federal agencies, had been in negotiations with the Trump Organization to formalize a lease of that space when the deal collapsed. The two parties had gone as far as drawing up a lease contract, the two people privy to the negotiations said. But representatives of the Trump Organization refused to sign it over objections to the inclusion of a clause in the contract, the contents of which were not immediately known.

It also was not immediately clear why the Trump Organization objected to the clause.

Amanda Miller, a spokeswoman for the Trump Organization, did not address that account. She merely said both parties had agreed the agency should look elsewhere. “After much consideration, it was mutually determined that it would be more cost effective and logistically practical for the Secret Service to lease space elsewhere,” she wrote in an email.

Pamela A. Dixon, a spokeswoman for GSA, declined to comment.

Catherine Milhoan, a spokeswoman for the Secret Service, said today that the relocation had no impact on the agency’s security plan and that the agency still hoped to find an acceptable space.

“The United States Secret Service continues to work with GSA to obtain permanent work space in an appropriate location,” she said.

The Washington Post first reported the fallout from the leasing dispute today.

Though Trump has not visited the 58-floor tower since his inauguration, the Secret Service continues to have a significant role there. The agency is required by statute to protect a president’s primary residence, regardless of whether any members of the first family are there or not.

The agency’s presence has diminished since Melania Trump, the first lady, moved to Washington this summer. But with a mix of retail, commercial and residential space in the tower and two of the agency’s protectees, Donald Trump’s two adult sons, regularly at work there, it still requires significant resources.

The Secret Service, like other government agencies, relies on GSA to negotiate real estate transactions. It provides GSA with a list of specifications, like square footage, location and other technical requirements, needed for its operations, an agency official said. Those requests are negotiable, however.

GSA negotiated a separate, successful lease on behalf of the Defense Department in April to be used by the White House Military Office. The 3,475-square-foot space is privately owned, so Trump’s company will not directly benefit from the government lease. It costs $130,000 a month.