A billboard supporting Egyptian President Abdel-Fattah el-Sissi in the presidential election scheduled for March hangs in downtown Cairo. Picture: Amr Nabil/AP

Cairo - Egypt's incumbent President Abdel-Fattah al-Sissi will most likely become the only candidate in the country's presidential election on Monday after a string of would-be challengers pulled out or were barred from running.

The deadline for candidacy registration is 2 pm (1200 GMT). The election is due be held over three days starting on March 26.

On Saturday, al-Wafd, Egypt's oldest liberal party, refused to let its leader run for president. Al-Wafd had earlier announced backing al-Sissi to seek a second term in office in the election.

Barring a last-minute submission, it will be a one-horse race, similar to other presidential elections in the decades before the 2011 revolt, which toppled long-time autocrat Hosny Mubarak.

The current situation brings the possibility of a low voter turnout.

Last week, presidential hopeful Sami Annan, a former military chief of staff, was barred from running after the army summoned him for investigation over possible breaches of army regulations that ban active officers from contesting elections.

In recent weeks, three other potential contenders have withdrawn their bids.

Opposition rights lawyer Khaled Ali dropped out of the race, accusing authorities of harassment and the election commission of bias against him.

Former prime minister Ahmed Shafiq, who had been widely seen as a serious challenger to al-Sissi, said he would not run for president, reversing an earlier announcement.

Former lawmaker Mohammed Anwar Sadat also quit, citing fears that his supporters could be arrested or intimidated by authorities. 

Al-Sissi, an ex-army chief, came to power in 2014, a year after he led the overthrow of the country's first democratically elected but divisive Islamist president Mohammed Morsi.