Washington, Apr 25 (IANS): Mitt Romney has swept five Republican primaries to effectively clinch the Republican nomination to challenge President Barack Obama in the November general election.

With his nearest rival, Rick Santorum out of the race, the former Massachusetts governor built up a big lead in delegates with victories Tuesday in Connecticut, Delaware, New York, Pennsylvania and Rhode Island.

"A better America starts tonight," Romney told a cheering victory rally in New Hampshire. "The last few years have been
the best that Barack Obama can do, but it's not the best America can do.

"Tonight is the beginning of the end of the disappointments of the Obama years and it's the start of a new and better chapter that we will write together," he said.

Far ahead of the field in the battle for delegates, Romney became the presumptive nominee April 10 after former senator Santorum of Pennsylvania, suspended his campaign.

Even though former House Speaker Newt Gingrich and House of Representatives member Ron Paul of Texas continue their long-shot bids for the White House, the party appears to be consolidating around Romney.

According to a CNN estimate, Romney has 695 of the 1,144 delegates needed, with Santorum holding 273 delegates, Gingrich 141 and Paul 72.

By CNN's count, the earliest Romney could reach the nomination threshold is late May, while Obama already has clinched the Democratic nomination, as expected.

Romney needs to overcome a big Obama advantage among young voters. In 2008, voters ages 18 to 29 supported Obama over Republican nominee Senator John McCain by 66 percent to 32 percent, according to CNN exit polling.

Obama has maintained his lead among the group, according to the latest CNN/ORC International Poll, with 64 percent support to Romney's 32 percent.