WASHINGTON?The US Senate on Saturday blocked a White House-backed bill to offer a path to citizenship to young undocumented immigrants who attend college or enroll in the military.

Lawmakers voted 55-41, largely along party lines, to end debate on the Development, Relief and Education for Alien Minors (DREAM) Act, falling short of the 60 votes needed to advance the bill and effectively killing it.

Some of President Barack Obama's Democratic allies sided with most Republicans to defeat the measure, which opponents had branded as amnesty.

Supporters of the bill, which was a top priority of Democratic Senate Majority Leader Harry Reid, said it was wrong to punish people brought to the United States by undocumented parents and emphasized that the legislation included safeguards and set high hurdles to citizenship.

"It is disappointing that common sense did not prevail today," Obama said in a terse statement, adding that while the House of Representatives passed it last week, a "minority of senators" killed the bill in the Senate by refusing to vote to end debate, essentially letting it languish.

"But my administration will not give up on the DREAM Act, or on the important business of fixing our broken immigration system," Obama added.

"The American people deserve a serious debate on immigration, and it's time to take the polarizing rhetoric off our national stage."

The measure would have offered legal residency to undocumented immigrants under 30 who arrived in the United States before they were 16, have lived on US soil for five years and have not committed serious crimes.

Eligible immigrants would have also had to have graduated from high school and either attended college or served in the US armed forces.

Obama said the legislation was key to US economic competitiveness and military readiness, and that the act would have slashed the ballooning deficit by 2.2 billion dollars over 10 years.

After repeated efforts failed to secure a comprehensive overhaul of the tattered immigration system in the United States ? where some 11 million undocumented people reside ? the bipartisan bill had sought to better integrate children brought illegally to the country by their parents.

But Republicans criticized it as "amnesty" for illegal immigrants.

Senator Jeff Sessions of Alabama on Saturday denounced the failed bill as a "reward for illegal activity," saying it would "put illegal aliens in front of the line ahead of those who patiently waited and played by the rules."