D.C. Mayor Walter E. Washington testified yesterday that his longtime aide and political ally, Joseph P. Yeldell, had not told him about his personal financial ties with Dominic F. Antonelli Jr. at the time when Yeldell was negotiating with Antonelli over a city government lease.

The mayor appeared as a prosecution witness iN Yeldell's and Antonelli's bribery and conspiracy trial in U.S. District Court on a day when the prosecution also produced its first evidence about a $33,000 loan that Antonelli allegedly made secretly to Yeldell, as well as additional testimony about Yeldell's efforts to get Anotnelli the lucrative city government lease.

The mayor, dressed in a three-piece blue suit with a white handkerchief in his pocket, appeared relaxed as he testified under oath for 23 minutes. He spoke calmly and matter-of-factly, but frequently acknowledged that he only vaguely recalled some key events in 1975 and 1976. He later told a reporter this was his first appearance as a witness in a criminal trial during 11 years as the city's chief executive. Yeldell gazed at the mayor as he testified.

The mayor was asked by Assistant U.S. Attorney Richard L. Beizer whether he was ever told of Yeldell's personal financial relationship with Antonelli during the months preceding June 9, 1976, the date when the mayor approved Antonelli's proposed lease with the city. "No," he replied. "Not between the time periods you allude to." The mayor added that he learned of Yeldell's financial ties with Antonelli only later, after these began to be disclosed in the press.

Yesterday's testimony about the secret $33,000 loan to Yeldell was provided by Lawrence A. Sinclitico, an employe of Commonwealth Land Title Insurance Co., who told the jury that almost all the arrangements for the loan were initiated by Antonelli. Sinclitico, who drew up the loan documents in the name of a fictitious lender, or "straw," testified that he never talked with Yeldell about the loan and only once exchanged written correspondence with him.

At one point, Sinclitico's testimony appeared to raise possible doubt about Yeldell's previous assertions that he never knew the secret loan had been provided by Antonelli. Sinclitico testified that he informed Antonelli but not Yeldell, that an initial payment for settlement and other costs was due. Sinclitico said he soon received Yeldell's check for the amount, $657.95. "I don't know where it came from, but it was Mrs. Yeldell's check," Sinclitico added.

Additional evidence about Yeldell's efforts to clear the way for Antonelli's city government lease was provided by Acting D.C. Corporation Counsel Louis P. Robbins, who also appeared as a prosecution witness. Robbins recalled a meeting in Yeldell's office in May 1976, in which he was asked by Yeldell and Antonelli, who was also present, to reconsider his legal objections to Antonelli's proposed 20-year-lease.

Robbins and other lawyers in the Corporation Counsel's Office had opposed the 20-year term of the proposed least partly because, they contended, the city could not legally obligate itself for so long a lease for an old building.

At the meeting in Yeldell's office, Robbins testified, "Mr Antonelli stated that there would not be a consummation of the lease unless it could be entered into for a period of 20 years." Yeldell also supported the proposed 20-year term, arguing that the rent would be lower for a long-term lease and that the city would need the building for a long time. Robbins recalled.

Immediately afterward, Robbins testified, he met with his staff lawyers and decided to drop their earlier objections to the proposed 20-year term.

Among other objections that were raised by the Corporation Counsel's office over the proposed lease, according to testimony yesterday, was the absence of a ceiling on city expenses for rising maintenance and other operating costs for the building. When Antonelli was told of this objection, Assistant Corporation Counsel Semi Feuer testified yesterday, "He [Antonelli] indicated that he would speak to Mr. Yeldell about that."

The lease negotiations are central to the charges on which Yeldell, who is now on unpaid leave from his most recent job as a top mayoral aide, and Antonelli, a millionaire parking executive and real estate developer, have been indicted.

Antonelli and Yeldell, who at the time headed the city's huge Department of Human Resources, are alleged to have conspired in corruptly arranging a $5.6 million DHR lease for a two-story office building at 60 Florida Ave. NE that was eventually purchased from its previous owner by a partnership controlled by Antonelli. In return for the lease, Antonelli is accused of giving Yeldell the secret $33,000 loan after previously helping him obtain another $21,500 loan from a bank in which Antonelli is a major stockholder.

Mayor Washington's testimony was sought by the prosecution to help support its allegation that Yeldell had illegally concealed his personal financial relations with Antonelli from District government officials and the public. In memorandums this week, prosecutors have argued that Yeldell was required to disclose his ties with Antonell under existing city laws, while defense lawyers contended that no such disclosure was necessary.

In his cross-examination of the mayor, Antonelli's chief defense lawyer, Edward Bennett Williams, drew some statements to support defense assertions that one of Yeldell's alleged actions - his efforts to obtain independent leasing powers for DHR - was prompted by legitimate causes, rather than by Yeldell's allegedly corrupt attempts to secure the Florida Avenue lease for Antonelli's partnership.

The mayor told the jury that his decision in late 1975 to give DHR its own leasing, contracting and purchasing powers - authority previously held by the D.C. Department of General Services - stemmed from what he believed were severe difficulties in ordering drugs and leasing X-ray equipment at D.C. General Hospital, then a DHR subsidiary. The mayor asserted later that he "acted to get the medicine there so you could prevent lives from being lost."

Sinclitico, the Commonwealth Land Title Insurance Co. employe who helped arrange Antonelli's secret loan to Yeldell, testified that Antonelli had initiated the loan in early 1976, by asking him to conduct a title search on Yeldell's home. "We were at the [Touchdown] Club one night, and he [Antonelli] asked me to run a title on it, "Sinclitico said, describing himself at a longtime friend of Antonelli.

Sinclitico testifed that Antonelli instructed him to use the $33,000 proceeds of the loan to Yeldell to pay off two of Yeldell's outstanding bank debts, including a loan from Madison National Bank, in which Antonelli is a major stockholder. Sinclitico told the jury that Yeldell's monthly $330 payments on the $33,000 loan were turned over to him and that he later passed money along to Antonelli.

The loan, secured by a second mortgage on Yeldell's house, was listed in the fictitious name of John Halloran, Sinclitico testified. Antonelli "just told me to use any straw," he said.

Two other witnesses testified yesterday about Antonelli's efforts to secure the Florida Avenue lease from Yeldell's agency.

William S. Harps, a real estate appraiser who was eventually retained by DHR to draw up a report on the 60 Florida Ave. NE building, testified that he received a telephone call in February 1976, from one of Antonelli's lawyers, Mitchell Blankstein, even before Harps was hired by the city. Blankstein, Harps said, arranged for him to inspect the Florida Avenue building and review the building's financial and other records.

On March 6, 1976, two days before he signed his consulting contract with the city, Harps testified, he went to Antonelli's office to examine the Florida Avenue building records. "Mr. Blankstein was there, and from time to time, Mr Antonelli came into the room," Harps said."We had plans laid out there."

Another witness, Wallace B. Agnew, a real estate broker, testified that Antonelli had asked him in February 1976, whether he would be interested in becoming a consultant or negotiator for Yeldell's agency, DHR. Agnew at the time represented People Drug Stores, the previous owner of the 60 Florida Ave. NE building that was eventually bought by Antonelli's partnership and leased by DHR.

Agnew said he had rejected Antonelli's suggestion because of his prior role as Peoples' agent in the deal. But he added that he mentioned to Antonelli three other possible real estate consultants for DHR, two of whom were allegedly hired later by Yeldell.