"I announce in front of you from here, the province of Menoufia, that I have decided to nominate myself for the presidential elections,
"I will seek to win the trust and support of the people for a new term," said Mubarak on Thursday.
"I have embarked on a journey in which I will not falter before I complete it."
An official at the headquarters of Mubarak's ruling National Democratic Party said the president would be officially nominated later on Thursday as the party's candidate for the upcoming polls.
The official was not authorized to reveal the information, and declined to be identified.
Mubarak also promised constitutional and legislative changes during his next six-year term.
An anti-terrorism law should replace the emergency law, in force for 24 years and a major grievance of the political opposition and of human rights groups, he said.
Other changes would reduce the powers of the president and strengthen the role of the cabinet, he added.
He promised that as head of state he would ensure that the September elections would be "competitive, free and fair".
Mubarak, 77 and in power since 1981, made the announcement in the secondary school where he studied as a child, in the Nile Delta province where he was born in 1928.
Mubarak, who dominates the Egyptian political scene, is not expected to face a serious challenge in the elections, and the opposition says it doubts his commitment to reform.
"I will seek to win the trust and support of the people for a new term"
The rules exclude a candidate from the Muslim Brotherhood, the Islamist group which is the largest opposition force in the country of 72 million.
Mubarak's most prominent rival will probably be Ayman Nur of the liberal Ghad (Tomorrow) Party, who was detained in January and is now on trial on forgery charges.
Nur says the charges are politically motivated to undermine his campaign.
The presidential election campaign formally begins on 17 August, but Mubarak began his speech by recounting the achievements of his first 24 years in office and promising to do more.
Muhammad Habib, deputy leader of the Muslim Brotherhood, said he was sceptical that much would change.
Ayman Nur is the most prominent
rival of Mubarak in the polls
"We are faced with statements and words upon which we do not hang much hope. We hang our hopes on actions. We see that there is an insistence on working with emergency laws," he said after Mubarak made his speech.
"They have no real intention to take steps towards political reform," he added.
"Mubarak is not committed to reform and all of this is just embellishment," said Hisham Qasim, president of the Egyptian Organisation for Human Rights.
The main leftist party, the Tagammu, has decided to boycott the elections, saying the ruling party and authorities had already shown they did not plan to play fair.
The state media, for example, have largely ignored the activities of opposition groups while continuing to give extensive coverage of all President Mubarak's engagements.