Egypt's former prime minister Ahmed Shafiq said on Sunday that he will not now be a candidate in this year's presidential election, reversing a previous pledge to stand.

His decision to step aside is likely to pave the way for the poll to be dominated by incumbent Abdel Fattah al-Sisi.

The National Elections Authority is expected to announce a date for the election on Tuesday.

Shafiq's decision not to stand came after he was returned to Egypt last month from the United Arab Emirates, where he had lived in exile since 2012.

"I have decided to not run in the upcoming 2018 presidential elections," Shafiq said in a statement posted online.

"I saw that I will not be the best person to lead the country in the coming period."

Shafiq was appointed premier by former president Hosni Mubarak shortly before he was toppled in 2011. He was seen as a main challenger for Sisi who has not yet officially announcing his candidacy but is expected to cruise to a new term.

"His withdrawal from the elections might be leaving the scene void of any strong personality that can challenge President Abdel Fattah al-Sisi," said Mustapha Kamel al-Sayyid, a political science professor at Cairo University.

- Deported from UAE -

Shafiq announced his plan to stand in a November 29 video from the UAE, saying that it seemed Egypt needed "new blood" to face "many problems in all aspects of life".

After angering his Emirati hosts by saying in a video first aired by Al-Jazeera that he was being prevented from leaving the country, his aides said he was deported on December 2.

After arriving in Egypt, Shafiq disappeared for around 24 hours before reemerging to tell a talk show host he was reconsidering his bid for the presidency.

On Sunday Shafiq appeared to have dramatically changed his tune on the situation in Egypt.

Being in exile "may have kept me away from carefully following updates in the homeland, of progress and accomplishments," he said.

Shafiq narrowly lost out on the presidency in 2012 to Islamist president Mohammed Morsi.

After the election he was tried in absentia on corruption charges, and was eventually acquitted.

Sisi, a former army chief, was elected president in 2014, a year after leading the military's ouster of Morsi.

"Shafiq was considered a strong potential candidate to challenge President Sisi as he enjoyed popularity when he ran in the 2012 presidential elections," Sayyid said.

"Perhaps many people are nostalgic for the days of Hosni Mubarak, who see Shafiq as a continuation of Mubarak's rule. That's why it was expected he would attract a large number of voters," he said.

Other potential candidates may not be able to be muster similar interest, Sayyid added.

- Other candidates -

Such candidates include Khaled Ali, a rights lawyer and presidential candidate in 2012 who challenged the government over Red Sea islands Egypt gave to Saudi Arabia.

In November, Ali announced his intention to stand again in 2018.

However, he had been sentenced in September in absentia to three months in jail on accusations of "offending public decency", a ruling he appealed.

This was in relation to a photograph, that Ali says was fabricated and that appeared to show him making an obscene gesture while celebrating a court ruling in the case of the islands' transfer to Saudi Arabia.

Ali said only the committee organising the election can decide whether that ruling would disqualify him as a candidate.

Another presidential hopeful, military colonel Ahmed Konsowa, was given six years in prison in December by a military court after the previous month announcing his intention to stand.

Konsowa's lawyer said his client was given the jail sentence for stating political opinions while still in the military, even though Konsowa said he had been trying to resign from the military for more than three years.

Lawyer Asaad Heikal said Konsowa had only followed Sisi's example in announcing his candidacy. Sisi was in uniform when he did so, before later resigning as defence minister.