WASHINGTON - The Trump administration is seeking to delay a Democratic effort to require the Secret Service to disclose how much it spends protecting President Donald Trump and his family when they travel - until after the 2020 election, according to people familiar with the discussions.

The issue has emerged as a sticking point in recent weeks as Treasury Secretary Steven Mnuchin and key senators have been negotiating draft legislation to move the Secret Service back to his department, its historic home.

Mnuchin has balked at Democratic demands that the bill require the Secret Service to disclose the costs related to the travel of the president and his adult children within 120 days after it is passed, according to people with knowledge of the talks. Mnuchin has agreed to Democrats' push for a requirement that the Secret Service report its travel expenses but wants such disclosures to begin next year.

In a statement, the Treasury Department confirmed that Mnuchin has been working with Secret Service Director James Murray and congressional committees on a bill to transfer the Secret Service from the Department of Homeland Security to the Treasury, but it did not address the dispute about the reporting requirement.

"Conversations about the return of the Secret Service to the Treasury Department are ongoing, and we decline to comment on individual aspects of those conversations," said a Treasury official, who like others spoke on the condition of anonymity because of the ongoing negotiations.

The administration's resistance to disclosing how much taxpayer money has been spent on presidential travel has drawn criticism from Democrats, who say the public has a right to know the price of his frequent visits to his resorts in Florida and New Jersey.

During the 2016 campaign, Trump promised to "rarely leave the White House" and cut back on what he called wasteful travel by his immediate predecessor, Barack Obama.

Since taking office, however, Trump has made more than 50 visits to his properties outside the Washington area, according to a tally kept by The Washington Post.

The government spent about $96 million on travel by Obama over eight years, according to documents obtained by the conservative group Judicial Watch. A report by the Government Accountability Office, which serves as the congressional watchdog on federal spending, estimated that Trump's travel cost $13.6 million in one month of early 2017. That total included the costs of travel for Secret Service and Defense Department personnel, and the costs of renting space and operating equipment such as boats and planes. If spending continued at that pace, Trump would have exceeded Obama's total expenses before the end of his first year in office.

The extensive international business travel and vacations of his grown children, with Secret Service agents in tow, as well as the expense the Secret Service incurs to secure numerous Trump properties, has added to the agency's financial strain, according to its budget requests.

Since their father was elected, Trump's sons Eric and Donald Jr. have made business trips to overseas locales including Ireland, Scotland, Dubai, Uruguay and India. In 2017, Eric Trump's visit to a Trump building under construction in Uruguay cost taxpayers $97,000.

But exactly how much the frequent travel of the president and his family has cost taxpayers is unknown.

A 1976 law allows the president to designate one primary residence outside the White House for the Secret Service to protect full-time. It also requires the agency to report to Congress semiannually the costs of securing that property. The measure did not anticipate a chief executive who regularly visited that one property, as well as multiple others.

The Secret Service has failed or been late in recent years to provide even those limited costs reports. The agency did not file such reports in 2016 or 2017, according to the GAO. They have been delayed in submitting subsequent reports, filing a recent report in November that was due in March.

Agency officials have cited staff changes as the reason for its failure to submit two years of reports.

The Secret Service did not respond to a question about its required reports. A representative declined to answer questions about the agency's spending on presidential travel, saying it does not discuss "protective means and methods."

The White House has also declined to share information with the GAO about how much it spends to coordinate Trump's travel. In March 2017, the office sought to tally the cost of Trump's frequent travel to Mar-a-Lago based on a question from Congress. But for two years, the White House Counsel's Office didn't answer questions about the costs associated with coordinating travel for the president, according to a GAO report.

Last year, Sen. Dianne Feinstein, D-Calif., and other Democratic lawmakers saw an opportunity to push for more transparency and strengthen the reporting law when Mnuchin began seeking bipartisan support for a bill to move the Secret Service, which the Treasury Department said would improve the agency's ability to carry out its mission.

Originally created by the Treasury in 1865 to help stop rampant counterfeiters, the agency was housed there until 2003, when it moved to the new Department of Homeland Security created in the wake of the Sept. 11 terrorist attacks.

"Secretary Mnuchin came to me last year with a proposal to move the Secret Service to the Treasury Department," Feinstein said in a statement. "As part of that effort, I proposed that the cost of presidential travel be included for greater transparency, accountability and oversight associated with protection during travel of presidents and their families."

Feinstein wants the Secret Service to make semiannual reports of its travel costs, beginning a few months after Congress authorizes its transfer, according to people familiar with the talks.

But in a Dec. 23 letter to the Senate Judiciary Committee, Mnuchin said he was strongly opposed to that requirement. Instead, he is seeking an annual report that begins in 2021.

His demand for the delay in reporting is likely to reduce Democratic support for the bill, according to people monitoring Mnuchin's proposal.

The available records about Trump's travel provide only snapshots of the costs to the public: The GAO, for instance, found that his first four trips to Mar-a-Lago in 2017 cost the Secret Service about $1.3 million each. (Other agencies also spent money on those trips, bringing the federal government's total spending to $3.4 million per visit to Mar-a-Lago.)

Trump has made 22 more trips to Mar-a-Lago since then, according to a Post tally. If the Secret Service's costs remained constant, that would mean more than $28 million in further spending by the Secret Service alone, and $75 million from the government in all - and just on a fraction of Trump's total travel.

Another snapshot came in March 2017, as the Secret Service was still adjusting to Trump's large family and frequent golfing trips. The agency asked Congress to add $60 million to its budget just to handle Trump's travel, according to internal agency documents reviewed by The Post.

The Secret Service has also disclosed how much it spends on golf carts, to protect Trump and escort him during his golfing outings. These carts - leased from third-party vendors, not Trump himself - have cost the government $588,000 since 2017, according to federal spending data posted online.

The Secret Service spent at least $250,000 at Trump's properties in the first five months of his term, according to records of federal charge card expenditures released last year to a watchdog group, Property of the People. The documents were released two years after they had been requested, after the group sued. It is not clear whether some of this spending was also counted in the GAO report.

The records released by the Secret Service last year give very little detail - saying only the date of the purchase, the dollar amount and the kind of Trump property involved. They do not give the reasons for the purchases.

The Washington Post's Tom Hamburger contributed to this report.