"We will continue the battle and, in time, when we are absolutely convinced that we cannot continue, we will then meet with our regional group and search for another candidate," Rosenthal told Radio Sonora.
Venezuelan officials, meanwhile, sent mixed signals about a possible consensus candidate.
Venezuelan General Alberto Muller Rojas, a top adviser to President Hugo Chavez, told AFP "neither of the two parties (Venezuela and Guatemala) will get the necessary votes."
He added that the impasse will end with "the election of an outsider."
But Rojas added that Venezuela would "not withdraw its candidacy as long as Guatemala does not withdraw its own."
Venezuela's UN ambassador, Francisco Arias Cardenas, however, ruled out a withdrawal by either country.
"That Venezuela withdraws because it has fewer votes? It's not possible because it would be admitting the veto power of the United States," he told Venezuela's VTV television.
"That Guatemala and Venezuela withdraw to search for a third candidate? That's not possible," Arias said from New York.
The UN General Assembly resumed voting on Thursday to pick between US-backed Guatemala and staunch US critic Venezuela.
In new rounds of balloting on Thursday, Guatemala continued to lead but again fell short of the two-thirds majority required to win the non-permanent council seat.
On Monday, one round of voting ended in a tie but Guatemala has led in all the other rounds.

Copyright AFP (Agence France-Presse), 2006