MONROVIA (Reuters) - Liberia’s Supreme Court on Monday put a presidential run-off on hold until the electoral commission can investigate claims of irregularities and alleged fraud in last month’s first round of voting.

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Former footballer George Weah was initially set to face Vice-President Joseph Boakai on Tuesday to determine who will replace Nobel Peace Prize laureate Ellen Johnson Sirleaf. A successful vote would be Liberia’s first democratic transfer of power in over 70 years.

But preparations for the second round were halted last week when the Supreme Court announced it was examining a complaint by the Liberty Party of third-placed candidate Charles Brumskine.

The Supreme Court’s order for a full investigation into the allegations could push back the run-off date by weeks or even result in a re-run of the first round.

“The NEC (National Elections Commission) is stopped and prohibited from conducting the run off election until the complaint filed by the petitioners is investigated by the NEC,” the Supreme Court ruling said.

Addressing the Supreme Court last week, Brumskine cited “gross irregularities” in the first round and accused NEC officials of fraud.

The NEC has denied wrongdoing and said the election was largely fair. International observers say they saw no major problems with the vote.

But a growing chorus of parties have expressed doubt about the vote, including Boakai’s ruling Unity Party, which last week accused Johnson Sirleaf, one of its own members, of trying to influence the vote. She rejected the allegation.

“The course we pursue is not about Charles Walker Brumskine. It is not about the Liberty Party. It is greater than all of us. It is about our country,” Brumskine said following the Supreme Court ruling.

Janga Kowo, Secretary General of Weah’s CDC party, called upon supporters to remain calm and allow the legal process to run its course. The Unity Party had no immediate comment on Monday’s ruling.

Expectations of a poll delay have increased tensions in Liberia, where many are eager for change after 12 years of Johnson Sirleaf’s rule. Her tenure cemented peace after a long civil war, but many Liberians say she did little to alleviate widespread poverty despite vast iron ore reserves.

It is now unclear when the run-off will take place.

The NEC has until mid-November to rule on the Liberty Party’s complaint. If it is rejected, Brumskine could still take the case back before the Supreme Court with an appeal, potentially pushing the date of the second round into December.

The court also has the option of calling a new first round vote to be held within 60 days.