* Obama vows to push again for 'Dream Act'
* Young Hispanics watch vote in Senate Gallery (Updates with Obama comments, reaction)
WASHINGTON, Dec 18 (Reuters) - A controversial measure providing a pathway to citizenship for illegal immigrants who came to the United States as children was dealt a death blow in the U.S. Senate on Saturday by Republicans who said it would reward illegal activity.
The so-called "Dream Act" passed the U.S. House of Representatives earlier this month, but it failed to gain the 60 votes necessary to overcome opposition in the 100-member Senate.
President Barack Obama and Democratic supporters vowed to push again for the measure in the new Congress that will be seated in January.
"It is disappointing that common sense did not prevail today," Obama said in a statement. "But my administration will not give up on the DREAM Act, or on the important business of fixing our broken immigration system."
The legislation would have provided legal residency to young people who came to the United States illegally before age 16 and who graduated from high school, completed two years of college or military service and had no criminal record.
"They believe in their heart of hearts this is home, this is the only country they have ever known. All they're asking for is a chance to serve this nation," said Democratic Senator Dick Durbin, the measure's sponsor.
The measure was backed by Hispanic activists, who have been disappointed by Democrats' failure to deliver on Obama's promise of comprehensive immigration reform.
"The Senate has made a huge mistake today. It has failed to recognize the contributions of thousands upon thousands of bright, creative young people that love this country like their own home," Jorge-Mario Cabrera, an activist with the Coalition for Humane Immigrant Rights of Los Angeles, told Reuters.
Maria Rodriguez, and activist with the California DREAM Network, said: "The future doctors, lawyers, astronauts, chefs, and attorneys waiting for this vote to become a reality will continue to remain in the shadow and afraid to show America their beauty and skills."
With dozens of college-age Hispanics watching from the gallery, the measure failed on a largely party-line vote of 55-41. Although it gained a majority, the bill needed to reach a 60-vote threshold to advance in the 100-seat Senate.
Republicans said the bill would have made it more difficult to enforce immigration laws.
"The American people are pleading with Congress to enforce our laws, but this bill is a law that at its fundamental core is a reward for illegal activity," said Republican Senator Jeff Sessions.
The bill's failure to pass the Senate means the legislation dies with the 111th Congress. Supporters will face a steep uphill battle when the new Congress is seated on Jan. 5 and Republicans control the House and have a greater say in the Senate.
In his presidential campaign in 2008, Obama pledged to push for an immigration overhaul, boosting border security and offering steps to legal status for many of the nearly 11 million illegal immigrants living in the United States. His administration and Congress have so far failed to agree on comprehensive measures. (Reporting by Donna Smith, Andy Sullivan, and Tim Gaynor in Arizona; editing by Eric Walsh and Mohammad Zargham)