Islamabad: Two presidential candidates were today chosen by Pakistan's warring factions of the Opposition alliance which failed to reach a consensus on fielding a joint nominee, giving an upper hand to Prime Minister Imran Khan's pick for the post of the President, according to a media report.

Pakistan Peoples Party's (PPP) Aitzaz Ahsan and Jamiat Ulema-i-Islam (JUI-F) chief Maulana Fazlur Rehman emerged as the two candidates who will challenge Pakistan Tehreek-e-Insaf's (PTI)  Dr Arif Alvi in the election of September 4, Dawn newspaper reported.

The Election Commission of Pakistan had announced on August 16 that the presidential election will be held on September 4 - five days before the expiry of the five-year term of President Mamnoon Hussain.

The failure of the opposition parties to field a joint candidate will virtually provide a walkover to the ruling PTI's Alvi for the president's office, the report said.

While Ahsan filed his papers for the presidential election hours before the 12-noon deadline today, a JUI-F spokesperson claimed that Fazl would be the single nominee of the opposition parties, with the exception of the PPP.

The JUI-F chief will submit his nomination papers shortly as the joint candidate of the Pakistan Muslim League-Nawaz (PML-N), Muttahida Majlis-i-Amal (MMA), Awami National Party, Pakhtunkhwa Milli Awami Party and National Party, the spokesperson was quoted as saying  by the report.

The PPP and the PML-N representatives directly and with the help of mediators remained in touch throughout yesterday in their bid to reach an understanding, but all their efforts failed after the PPP's refusal to withdraw Ahsan's name, the report said.

The PML-N's acting secretary general Ahsan Iqbal, however, said that they had been still making all-out efforts to bring a joint opposition candidate, expressing the hope that the PPP might show "flexibility".

PTI nominated Alvi as its candidate hours after party chief Khan was sworn in as the 22nd prime minister of the country on August 18.

A dentist by profession, 69-year-old Alvi is one of the founding members of PTI. He served as the party's secretary general from 2006 to 2013.

Pakistan's president is elected indirectly by the members of Parliament and the four provincial assemblies.

The final list of contesting candidates will be issued on August 30.

The polling will be held in the buildings of the federal parliament and provincial assemblies.

In Pakistan, the President is considered as a symbol of the federation and head of the state and exercises all powers on the recommendations of the prime minister.

Hussain, elected in September 2013, was a nominee of the PML-N led by jailed former prime minister Nawaz Sharif.