A ruling on an appeal by Turkey's AK Party (AKP) calling for a re-run of the Istanbul mayoral election will be made on Monday by the High Election Board (YSK), the AKP's candidate said.
The main opposition Republican People's Party (CHP) won control of the capital Ankara and Istanbul, the country's biggest city, for the first time in 25 years in March 31 local elections.
President Tayyip Erdogan's AKP and their nationalist MHP allies have called for the results in Istanbul to be annulled and re-run citing what they say are irregularities.
The YSK has ordered recounts across Istanbul and in its interim ruling it ordered district electoral officials to inspect their respective polling station officials.
"The YSK has examined our party's and the MHP's objections to the Istanbul election results. I believe it will make a decision tomorrow," said AKP candidate Binali Yildirim, a former prime minister.
He spoke to reporters after morning prayers on Sunday, the first day of the Muslim holy month of Ramadan.
On Saturday, Erdogan signalled he favours a re-run of the Istanbul elections, which he said were marred by controversy and irregularities, adding that renewing the vote would allow the YSK to "clear its name".
Istanbul's new CHP mayor, Ekrem Imamoglu, said on Saturday that the objections were unreasonable and that they could "only laugh at this". CHP leader Kemal Kilicdaroglu has said the Istanbul elections had turned into a test for Turkish democracy.
Erdogan had accused the opposition of supporting "terrorism" and labeled the local election a "matter of survival" for Turkey during his campaign, which was held amid growing disenchantment among voters over economic woes.
The uncertainty over the results in Istanbul, which accounts for around a third of the country's economy, has kept financial markets on edge, as Turkey tries to recover from a currency crisis that saw the lira lose more than 30 percent of its value last year.