UNITED NATIONS – One asset Mark Malloch Brown brought to the office of chief of staff at the United Nations, where he has served since earlier this year, was his ability to charm both political parties in Washington, D.C. But for some Republicans, a rental arrangement Mr. Malloch Brown set up with financier George Soros could raise red political flags.

Mr. Malloch Brown, a Briton who lived in D.C. while working as a political consultant and later as a World Bank official, moved his family to the New York area two years ago. Looking for a place to rent with his wife, Patricia, and four children, Mr. Malloch Brown turned to his friend Mr. Soros, who offered the house next door to his own in the Westchester County town of Katonah. Mr. Soros owns both properties.

Both sides say Mr. Malloch Brown’s $10,000-a-month rent is at market rate for the five-bedroom house on a 4.8-acre lot. In 2001, before Mr. Malloch Brown and his family moved there, it was rented for $12,500 a month, according to the Multiple Listing Service. Mr. Soros’s spokesman, Michael Vachon, however, said that unlike Mr. Malloch Brown’s arrangement, the previous tenant’s rent covered utilities, which currently are paid by Mr. Malloch Brown.

The $120,000 annual rent is almost equal to Mr. Malloch Brown’s current annual net salary as undersecretary general – $125,000, according to U.N. records. William Orme, a spokesman for the United Nations Development Program, which Mr. Malloch Brown has headed since 1999, said Mr. Malloch Brown’s savings, including those from his time as a political consultant, cover the rent.

The house, on a chic street in Katonah, is Mr. Malloch Brown’s primary residence, making for about an hour-and-a-half commute by car to and from Turtle Bay.

“They are good friends,” Mr. Orme said of his boss and Mr. Soros. But since both are public figures, they decided to set up the living arrangement as a commercial transaction, rather than a gift,” Mr. Orme said.

“There is nothing untoward in this arrangement,” Mr. Soros’s spokesman, Mr. Vachon, said.

Both parties had good reason to keep the arrangement, as Mr. Vachon put it, “on the up-and-up.” The UNDP and the Soros-funded Open Society Institute cooperate on many projects, particularly in Central and Eastern Europe. Any whiff of an exchange of favors would be seized on by the development project’s detractors. In America, Mr. Malloch Brown must cultivate ties with Republicans, who dominate Washington, and many among them see Mr. Soros as an enemy.

Living arrangements that smack of gifts have created problems for other public figures. The 1998 nomination of Richard Holbrooke to be President Clinton’s U.N. ambassador was held up for almost a year in a Senate confirmation hearing. One reason was the battle over the propriety of Mr. Holbrooke’s rent during his time in New York – specifically, the allegation that a former American ambassador to Switzerland, the late Larry Lawrence, paid Mr. Holbrooke’s rent.

Separately, in the current Senate battle for U.N. ambassadorship, President Bush has found an unexpected ally in Mr. Malloch Brown, who has been telling reporters that the president’s choice, John Bolton, would make an excellent U.N. ambassador. Meanwhile, Mr. Soros has helped to buy TV ads in crucial states, trying to convince Republican senators to kill Mr. Bolton’s chances.

They don’t have to share an agenda, the spokesmen for both men said. “Mr. Malloch Brown also has many Republican friends, like Paul Wolfowitz,” Mr. Orme said.

The rental arrangement, however, raises the profile of Mr. Malloch Brown’s friendship with Mr. Soros.

“If true, this will be deeply troubling to Congress,” the Heritage Foundation’s Nile Gardiner said when told by The New York Sun about Mr. Malloch Brown’s living arrangement. It “raises serious concerns over the partisan political ties of U.N. officials, which should be fully disclosed,” Mr. Gardiner, who is a frequent critic of the U.N., said.

Mr. Annan’s closest American advisers have Democratic leanings, and Mr. Malloch Brown’s appointment as chief of staff in January occurred immediately after a meeting of American friends of Mr. Annan at Mr. Holbrooke’s home, where practically all the participants were close to the Democratic party.

Since letting Mr. Soros’s property in Katonah, Mr. Malloch Brown has continued to travel to Washington, where criticism of the United Nations has led to several legislation initiatives – culminating, most ominously for his employer, with the U.N. Reform Act of 2005, which is expected to pass on Friday in the House of Representatives. In addition to that act, which includes the possibility of withholding 50% of dues America pays to the United Nations, several Republican lawmakers have called for Mr. Annan’s resignation.

Mr. Malloch Brown has made a point to visit and disarm Turtle Bay’s most adamant critics, particularly Republicans.

“I thought that he was a charming man,” Rep. Dana Rohrabacher, a Republican of California, told the Sun in February after a personal meeting with Mr. Malloch Brown, indicating, however, that he had not been overly convinced by Mr. Malloch Brown’s pro-U.N. sales pitch.

At the same time, Mr. Soros, who has donated heavily to Senator Kerry’s presidential campaign last year and to such political organizations as Moveon.org, is the epitome of anti-Republicanism and anti-Bushism.