With complications delaying the selection of key Reagan Cabinet members, Vice President-elect George Bush and other top Reagan advisers were given use of the White House Situation Room Thursday night for a conference call over secure telephone lines to President-elect Ronald Reagan, who was in his California home.

No members of President Carter's staff were present at the session, according to informed sources. Among those who attended, in addition to Bush, were Reagan's top two staff advisers, Edwin Meese III and James A. Baker III, and Sen. Paul Laxalt (R-Nev.).

The session was held amid concerns over the possible nomination of retired general Alexander Haig to be secretary of state because of his assistance to former president Richard Nixon in the aftermath of the Watergate scandal, and the arrangements of Nixon's presidential pardon.

The subject of the conference call to Reagan -- and in fact, the existence of the call -- was being treated as a highly sensitive matter by top Reagan officials. But the subject discussed was apparently the latest complications in the selection of the Reagan Cabinet. Two senior officials, when asked about the nature of the call, responded by saying that they could not say anything about the Cabinet selection process.

Bush and Baker both declined to discuss the conference call. Said Bush: "I can't help you on this . . . I can't go into it." Laxalt confirmed that he was present in the Situation Room for the call to Reagan. But when asked if Haig's activities during the last days of the Nixon White House had been reviewed in the coast-to-coast call, he said he was "not at liberty to comment."

Reagan officials have also reportedly been concerned about their choice for secretary of treasury. Republican sources say complications have also arisen with the possible nomination for treasury secretary of Walter B. Wriston, chairman of Citicorp. Citibank, a subsidiary of the Citicorp holding company, has claims against Iranian assets and loans to troubled Chrysler Corp.

Reagan spoke to his top advisers in that Thursday night conference call over a secure telephone that had just been installed by the Army Signal Corps in his Pacific Palisades home, according to informed sources. Arrangements for use of the Situation Room had been made with Carter White House officials earlier Thursday by Meese, these sources said.