Republican presidential primaries are underway in five US states as the largest voting day since Super Tuesday takes place.

Mitt Romney is aiming for a clean sweep in New York, Pennsylvania, Connecticut, Delaware and Rhode Island earning
him scores of delegates on his way to becoming the Republican presidential nominee.

Romney is cruising towards the 1,144 delegates he needs to become the official Republican nominee who will challenge Democratic President Barack Obama in November's election.

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Newt Gingrich, Romney's nearest rival says he will "reassess his candidacy" if he does not win the state of Delaware, a recent focus of his campaign.

The Republican candidate told media he would reassess his candidacy depending on his finish in Delaware.

"I think we need to take a deep look at what we are doing," said Gingrich.

Current and former advisers to the Gingrich campaign paint a picture of a candidate who wants to stay in the campaign and, despite much evidence to the contrary, sees a path forward.A strong finish in Delaware, they said, would give Gingrich a reason to stay in the race until North Carolina votes, along with two other states, on May 8.

The two sides have already engaged in heavy combat and that will only increase in the six months of campaigning that are to follow until Americans vote on November 6 to decide whether to give the incumbent another four years or install a new leader.

Romney, the former Massachusetts governor has been the party's presumptive nominee since his closest rival, former Pennsylvania Senator Rick Santorum, dropped out of the race earlier this month.

Romney has currently has 698 delegates, and according to an AP count there are 209 more up for grabs in the latest round of primaries.

Al Jazeera's Alan Fisher reporting from Washington said: "It is a big day for Mit Romney, he is expected to win at least four out of five."

Source: Al Jazeera and agencies