Washington - With only 19 days left before presidential elections, Republicans are mounting challenges to voter registrations in key battleground states such as Ohio, where election officials have asked the US Supreme Court to intervene.

The challenges mostly involve newly registered voters, and would likely hurt Democratic nominee Barack Obama, whose campaign has worked to register huge numbers of new voters around the country.

In the Ohio case, Jennifer Brunner, secretary of state, late Wednesday asked the US Supreme Court to intervene in a disagreement over verifying voter eligibility, media reports said.

At stake are an estimated 200,000 of the 666,000 voters who have registered since January.

Brunner is appealing an order by the 6th US Circuit Court of Appeals in Cincinnati on Tuesday that agreed with the Ohio Republican Party that Brunner needed to set up a special database of newly registered voters whose driver's license numbers or Social Security numbers don't match records in other databases, the Cincinnati Inquirer reported online.

Republicans say they need the special database because the state system to verify voter registration information is too cumbersome for local officials to use.

Brunner argued in the filing that the ruling would create havoc on election day on November 4 and allow many voters to only cast irregular ballots, which could then be challenged later by election boards, the Washington Post reported.

Brunner said that the Republican Party had nearly two years to challenge the system and failed to do so, the New York Times reported.

Challenges to voter registration would hold up the final outcome in battleground states given the close nature of the race between Obama and Republican nominee John McCain.

Although Obama currently leads by a polling margin of more than 7 per cent, McCain got high marks for his debate performance Wednesday night. A last minute push in large battleground states that are normally Republican strongholds but are leaning to Obama, such as Virginia and Florida, could help put McCain in the White House.

The Ohio case follows a week of charges by Republicans against a community organizing group called ACORN, which has paid low-income workers, including recovered drug addicts, to sign up new voters among low-income groups. Obama, a former community organizer, has in the past worked closely with the group and McCain has attacked him for that association.

In Philadelphia, the deputy city commissioner told CNN that at least 1,500 newly registered voters signed up by ACORN were being challenged for irregularities. In Ohio, one ACORN worker had registered to vote 73 times in exchange for money and cigarettes, FOX News reported.

Obama's campaign has dismissed responsibility for faulty registrations by other groups and said that come election day, such discrepancies will be apparent when individuals show up to vote. (dpa)