WASHINGTON (AP) – Jeane J. Kirkpatrick, a political science professor whose support for Ronald Reagan conservatism catapulted her into the post of U.S. ambassador to the United Nations, has died at 80. She was the first woman to hold the post.

Initially a liberal Democrat, Kirkpatrick championed human rights, opposed Soviet Union communism and supported Israel.

“She defended the cause of freedom at a pivotal time in world history,” President Bush said Friday. “Jeane’s powerful intellect helped America win the Cold War.”

Secretary of State Condoleezza Rice called her a role model, “an academic who brought great intellectual power to her work.”

Kirkpatrick’s son, Stuart, said she died Thursday at her home in Bethesda, Md., where she was under hospice care. The cause of death was not immediately known. U.N. Ambassador John R. Bolton asked for a moment of silence for her at a meeting of the U.S. delegation to the U.N. in New York.

U.N. Secretary-General Kofi Annan praised “her commitment to an effective United Nations” and said Kirkpatrick was “always ardent and often provocative.”

Kirkpatrick’s health had been in decline recently, her assistant, Andrea Harrington said, adding that she had been going to work about once a week “and then less and less.”

Tributes flowed in:

“America has lost one of its pre-eminent statesmen,” said Sen. Chuck Hagel, R-Neb.

“Our country has lost a patriot and a class act,” said Rep. Tom Lantos, D-Calif.

“America has lost a clarion voice for freedom,” said Sen. Joseph Lieberman, D-Conn.

Kirkpatrick “helped change the course of history and bring down the Soviet Union,” former Rep. Jack Kemp, R-N.Y., said on CNN.

“She was a great believer in civil rights,” Kemp said. “She was a great fan of Dr. Martin Luther King.”

Named to the U.N. post by President Reagan in 1981, Kirkpatrick was known as a blunt advocate. She remained involved in public issues after leaving the government two decades ago.

She joined seven other former U.N. ambassadors in a letter advising Congress that a plan to withhold U.S. dues to force reform at the United Nations was misguided and would “create resentment, build animosity and actually strengthen opponents of reform.”

Kirkpatrick was a political science professor at Georgetown University from 1957 until her appointment as U.N. ambassador.

One of her more riveting moments at the United Nations occurred in September 1983 when she commissioned an audiovisual presentation there of the Soviet downing of a South Korean passenger plane, KAL007, that had strayed into Soviet airspace. All 269 persons aboard died.

Alvin A. Snyder, producer of the video, revealed in 1996 that unedited versions of the tape disclosed that the Soviets thought the aircraft was an American RC-135 reconnaissance plane.

Her support for Israel, particularly at the United Nations where the Jewish state often is denounced, was steadfast.

In 2002, at a seminar in Washington sponsored by the Zionist Organization of America, Kirkpatrick said a Palestinian state would be “a catastrophic mistake” and a danger to Israel. It would be appeasement, Kirkpatrick argued, and a step backward from the U.S. fight against terrorism.

Kirkpatrick helped found the Center for a Free Cuba in 1997. On her death, the group issued a statement paying tribute to her efforts to promote human rights and democracy on the island.

She also was a longtime member of the Freedom House board of trustees. “Her strong support for Freedom House and its mission reflected her fundamental commitment to the rights of men and women everywhere,” said Jennifer Windsor, executive director of the pro-democracy group.

Bill Bennett, secretary of education in the Reagan administration, said the Iraq Study Group, prominently in the news lately, “would have been better with Jeane Kirkpatrick on it. … She had no patience with tyrannies, said they had to be confronted, you couldn’t deal with tyrannies, that there were some people you could work with – these people you couldn’t.”

Kirkpatrick once referred to herself as a “lifelong Democrat.”

She actually switched to the GOP in early 1985, four years after Reagan sent her to New York for the U.N. job. She took with her a reputation as a hard-liner on foreign policy. Because of this, she often was a lightning rod for the opposition. In some respects, she shared Bolton’s controversial profile. Bolton recently said he would resign when it became clear the Senate would not approve him full-time as U.N. ambassador.

Describing his work with Kirkpatrick at the American Enterprise Institute, where she had been a senior fellow, Bolton told reporters Friday: “When I was at AEI in the late ’90s for most of that time our offices were right next to each other and. …”

His voice then broke, and, near tears, he closed his eyes briefly, cleared his throat and continued in a quavering voice, “I benefited very greatly. It really is very sad for America, but she will be greatly missed.”

In a speech to the Republican National Convention that nominated Reagan for a second term in 1984, Kirkpatrick castigated the Democrats as not blaming guerrillas and their Soviet allies “when Marxist dictators shoot their way into power in Central America.”

“They always blame America first,” she said.

Born Jeane Duane Jordan in Duncan, Okla., she was graduated from Barnard College in New York in 1948 and then received her master’s degree and doctorate from Columbia.

During her early academic career she was a Marxist and joined the youth section of the Socialist Party of America.

Kirkpatrick considered seeking the Republican presidential nomination that went to George H. W. Bush in 1988. She stopped that process short, however, retreating to the position that she would accept the No. 2 slot if asked.

She is survived by two sons, Stuart, a Buddhist minister in Ann Arbor, Mich., and John, a lawyer in Miami, Fla. A third son, Douglas, died earlier this year. Her husband of 40 years, Evron, died in 1995.