Afghan presidential candidate Abdullah Abdullah on Wednesday pulled out of an audit being conducted by the United Nations, or U.N., disrupting a process aimed at determining a successor to outgoing President Hamid Karzai. Both Abdullah and Ashraf Ghani Ahmadzai, the two leading candidates, have accused the other of rigging the election.

Abdullah's withdrawal from the election audit has halted the process and it is not clear when it will resume. Abdullah and Ahmadzai both claimed victory after the June 14 vote, followed by claims that the other had committed fraud during the polls, Agence France-Presse, or AFP, reported. It is feared that the stand-off between the leaders could trigger clashes between their supporters that could deteriorate into ethnic clashes across the country.

"We will not join the process today, and maybe we will not re-join the process at all," Fazel Aqa Hussain Sancharaki, a spokesperson for Abdullah's campaign, told AFP, adding: "Talks are ongoing with the UN. If that reaches an agreement, we will come back. If not, that is the end of it."

Abdullah’s supporters belong to the Tajik community, which comprises 27 percent of the total population while Ghani has the backing of Pashtuns, the majority community in the country, who make up 42 percent of the Afghan population.

The United States, which is preparing to withdraw a significant number of its troops by the end of 2014, has backed the audit and urged both leaders to accept its outcome. Moreover, the timing of the audit's interruption is also critical because Karzai has insisted that his successor be inaugurated next Tuesday, AFP reported.

"[The audit] is supposed to start without Abdullah's supporters," a Western official said, according to Reuters.