Former U.N. ambassador Jeane J. Kirkpatrick will announce Monday whether she will seek the Republican presidential nomination, a Kirkpatrick adviser said yesterday. "At this point, I don't know. It's 50-50," said the source, who asked not to be identified. He said Kirkpatrick has been "in a three-day vigil" that began Thursday night making telephone calls and meeting with supporters.

If Kirkpatrick decides to run, she will hold a news conference Monday and announce her candidacy without forming an exploratory committee. If she decides against the race, she will issue a statement, the source said. Some possible reasons for not running include the lateness of the date, loss of income from speeches and writing and, the source said, the fact that "this is not a nice process." He said money is not an issue: "We're confident we can raise the money to make a national race."

Why would Kirkpatrick run? "She is driven to serve her country," the adviser said. He also noted that the conservatives encouraging Kirkpatrick are disappointed in Rep. Jack Kemp (R-N.Y.). "Jack has not caught on. If he were the front-runner, she'd not get in the race," he said.

Kirkpatrick frequently has been mentioned as a vice-presidential possibility on the GOP ticket, and she said last week, "I'm not sure I would turn it down." But, according to the source, "If she runs, it will not be for the vice presidency, seriously."

Kirkpatrick has the support of some key New Hampshire conservatives, including former governor Meldrim Thomson Jr. and Gerald Carmen, a former chairman of the state Republican Party who ran Ronald Reagan's 1980 New Hampshire campaign. The Manchester Union Leader has looked kindly on a Kirkpatrick candidacy. Others encouraging Kirkpatrick to enter the race are pollster Arthur Finkelstein; Sophia Casey, widow of the late CIA director, and Lynn Meyerhoff, a longtime conservative activist and contributor from Maryland.

If Kirkpatrick announces that she is in the race, William F. Buckley has given his okay for Kirkpatrick to participate in the Public Broadcasting Service "Firing Line" debate -- the first full debate of the GOP candidates -- in Houston on Wednesday.