WASHINGTON (AFP) - Senator Barack Obama has cut into Hillary Clinton's lead in Pennsylvania ahead of the state's Democratic presidential primary later this month, according to a new poll published Tuesday.

Clinton, who needs a big win in the eastern state on April 22 to keep her campaign for the party nomination alive, leads rival senator Obama 50 percent to 44 percent, the Quinnipiac University poll showed.

Just last week the poll had Clinton leading Obama by nine points, and the former first lady had a 12-point lead in mid-March, according to Quinnipiac.

The poll, taken over April 3-6, showed Obama picking up women voters, a cornerstone of Clinton's support base.

Quinnipiac said that over the past week Clinton's margin of support among women supporters fell to 54 to 41 percent from 54 to 37 percent.

It also said Obama, vying to become the country's first African-American president, had cut into her support among white voters.

Clinton led among white voters 56 to 38 percent, down from 59 to 34 percent last week.

Obama led among black voters, 75 percent favor the Illinois senator while 17 percent back Clinton.

Clinton prevailed among voters over the age of 55 and Obama had the edge among those under 45.

The two Democrats are engaged in a tight race to amass enough delegates to win the party's nomination and contest the presidential election in November against Republican rival John McCain.

Obama currently leads the race nationally with 1,637 delegates compared to Clinton's 1,502, with 2,025 needed to win the nomination, according to the independent Real Clear Politics website. He also holds a narrow lead in the popular vote in nomination contests.

The poll showed Obama making inroads against Clinton in a state considered perfectly suited to his rival.

"Obama is not only building on his own constituencies, but is taking away voters in Senator Hillary Clinton's strongest areas -- whites including white women, voters in the key swing Philadelphia suburbs and those who say the economy is the most important issue in the campaign," said Clay Richards, assistant director of the Quinnipiac University Polling Institute.

With Clinton under pressure to score an impressive victory in Pennsylvania, Obama "needs only to come close to be considered the winner" as Clinton has argued she is best placed to compete in large, pivotal states against McCain, the presumed Republican nominee.

The survey of 1,340 voters was carried out from April 3-6 with a margin of error of 2.7 percent.