WASHINGTON (AP) - Solicitor General Elena Kagan will be

nominated Monday to the Supreme Court by President Barack Obama, a

person familiar with the president's thinking says, positioning the

high court to have three women justices for the first time.

Obama plans to announce his choice at 10 a.m. in the East Room

of the White House. The source spoke on condition of anonymity

because the decision, which came after a monthlong search, had not

been made public.

Kagan is known as sharp and politically savvy and has enjoyed a

blazing legal career. She was the first female dean of Harvard Law

School, first woman to serve as the top Supreme Court lawyer for

any administration, and now first in Obama's mind to succeed

legendary liberal Justice John Paul Stevens.

At 50 years old, Kagan would be the youngest justice on the

court, which would give her the opportunity to extend Obama's

legacy for a generation.

Kagan must first win Senate confirmation.

A source close to the selection process said a central element

in Obama's choice was Kagan's reputation for bringing together

people of competing views and earning their respect.

Kagan came to the fore as a candidate who had worked closely

with all three branches of government, a legal mind with both a

sense of modesty and sense of humor. The source spoke on condition

of anonymity to discuss factors that led to Kagan's impending

nomination.

Kagan has clerked for Thurgood Marshall, worked for Bill Clinton

and earned a stellar reputation as a student, teacher and manager

of the elite academic world. Her standing has risen in Obama's eyes

as his government's lawyer before the high court over the last

year.

Yet Kagan would be the first justice without judicial experience

in almost 40 years. All of the three other finalists she beat out

for the job are federal appeals court judges, and all nine of the

current justices served on the federal bench before being elevated.

Kagan's fate will be up to a Senate dominated by Democrats, who

with 59 votes have more than enough to confirm her, even though

they are one shy of being able to halt any Republican stalling

effort.

For the second straight summer, the nation can expected an

intense Supreme Court confirmation debate even though, barring a

surprise, Kagan is likely to emerge as a justice.

Supreme Court justices wield enormous power over the daily life

of Americans. Any one of them can cast the deciding vote on matters

of life and death, individual freedoms and government power.

Presidents serve four-year terms; justices have tenure for life.

Republicans have shown no signs in advance that they would try

to prevent a vote on Kagan, but they are certain to grill her in

confirmation hearings over her experience, her thin record of legal

writings and her objections to the military's policy about gays.

When she was confirmed as solicitor general in 2009, only seven

Republicans backed her.

Democrats went 15 years without a Supreme Court appointment

until Obama chose federal appellate judge Sonia Sotomayor last year

to succeed retiring Justice David Souter. Just 16 months in office,

Obama has a second opportunity with Kagan, under different

circumstances.

Obama's decision last year centered much on the compelling

narrative of Sotomayor, the first Hispanic Supreme Court justice,

who grew up in a housing project and overcame hardship.

This year, Obama particularly wanted someone who could provide

leadership and help sway fellow justices toward a majority opinion.

The president has grown vocal in his concern that the

conservative-tilting court is giving too little voice to average

people.

Kagan is known for having won over liberal and conservative

faculty at the difficult-to-unite Harvard Law School, where she

served as dean for nearly six years.

Her background, including time as a lawyer and a key domestic

policy aide in President Clinton's White House, would give the

court a different perspective.

The White House is expected to frame Kagan's lack of service as

a judge in upbeat terms, underscoring that there are many qualified

routes to the top of the judiciary.

Kagan, who is unmarried, was born in New York City. She holds a

bachelor's degree from Princeton, a master's degree from Oxford and

a law degree from Harvard.

She served as a Supreme Court clerk for one of her legal heroes,

Justice Thurgood Marshall. And before that, she clerked for federal

appeals court judge Abner Mikva, who later became an important

political mentor to Obama in Chicago.

Kagan and Obama both taught at the University of Chicago Law

School in the early 1990s.

In her current job, Kagan represents the U.S. government and

defends acts of Congress before the Supreme Court and decides when

to appeal lower court rulings.

Kagan has the high task of following Stevens, who leaves a

legacy that includes the preservation of abortion rights,

protection of consumer rights and limits on the death penalty and

executive power. He used his seniority and his smarts to form

majority votes.

Rick Garnett, a professor of law and associate dean of

University of Notre Dame Law School, voiced the concern of many

conservatives.

"Future elections might undo some of the president's policies,

but his more liberal views about the Constitution, the powers of

the national government, and the role of unelected federal judges,

are now being locked in securely," Garnett said in a statement.

Kagan would be the fourth woman to serve on the Supreme Court,

following current Justices Ruth Bader Ginsburg and Sonia Sotomayor

and retired Justice Sandra Day O'Connor.

She would be the third Jewish justice along with six Catholics.

With Stevens' retirement, the court will have no Protestants, the

most prevalent denomination in the United States.