The Muslim Brotherhood’s presidential candidate said Sunday that he reluctantly stepped into the race to cement the political ascendancy of Egypt’s most prominent Islamist group amid fears that the country’s ruling military chiefs could hijack the transition to democratic rule.

Khairat el-Shater, a multimillionaire who has been the Brotherhood’s chief financier and strategist, said the group reneged on its promise not to field a presidential candidate only to stop the “tyranny” of the past. The move followed the ruling military council’s refusal to allow the Brotherhood’s political party, which dominates Egypt’s new parliament, to appoint a new interim cabinet.

“We asked the military council to task the Freedom and Justice Party with the formation of a wide coalition government that includes all the political powers represented in parliament, headed by the party,” Shater said in a wide-ranging interview. “We were incessantly prevented from doing that.”

The Brotherhood’s Freedom and Justice Party has almost half of the seats in parliament, but, without any executive authority, “our popularity got eaten in the streets because we are unable to solve people’s problems,” he said.

Backed by the most organized and politically savvy movement in Egypt, Shater has a strong chance of becoming the first president of Egypt since Hosni Mubarak’s ouster in February 2011. But with Mubarak-era spy chief Omar Suleiman now in the race — he registered at the last moment on Sunday with more than 100,000 signatures of support — the election next month is shaping up to be a battle between a symbol of the Mubarak government and the candidate for the ascendant Muslim Brotherhood.

“We are talking about a nation that was subjected to destruction and plundering under Hosni Mubarak’s leadership, who based his system on tyranny and corruption, which led to backwardness, and Omar Suleiman was one of his main assistants,” Shater said Sunday. “His nomination is an insult to all the Egyptian people and an attempt to reproduce the old regime in a modified way.”

The ruling military council has promised to hand over power by the end of June to an elected president. But some worry that the generals will continue to work to protect their vast economic privileges. Many also accuse the military council of backing Suleiman as its candidate. Abdel Moneim Aboul Fotouh, a progressive Islamist candidate who was a senior member of the Brotherhood before severing ties to run for the presidency, said Sunday that he believed the generals had pushed Suleiman into the race and are “conspiring against the elections.”

Shater’s nomination, announced late last month after a fierce internal debate, has also triggered a storm of criticism from competing parties and candidates, as well as revolutionaries and some within the Brotherhood. The Freedom and Justice Party is already accused of having an unduly large presence on the assembly tasked with writing the new constitution. The decision to field two presidential candidates — Shater and a backup candidate, in case he is disqualified from the race — came after the group had promised for more than a year that it would not put forward a candidate, in an effort to allay fears of non-Islamist Egyptians and Western allies.

Shater was imprisoned during Mubarak’s rule because of his membership in the Brotherhood. Although Shater said he was pardoned by the military council after being released after last year’s revolt, he said he worries that the “old fabricated cases” could be used to stop him from running.

Under the leadership of the Muslim Brotherhood, Egypt will become a modern and democratic state using Islam as the main point of reference, as capitalism and liberalism were for the United States and Marxism was for the former Soviet Union, Shater said. Islam would guide the nation’s social, economic and political life in a general sense, while leaving the details of religious practice for people to decide for themselves. “Our project is trying to build Egypt’s renaissance with an Islamic reference,” he said. “We are talking generally about providing the most possible amount of justice, freedom and dignity for the Egyptian person and preserving their right to a dignified life.”

Shater said the United States should support the democratic transition in Egypt, calling it “an important strategic relationship.” Mubarak’s Egypt was Washington’s staunchest ally in the Arab world, and America’s blind support for the autocrat during his reign has hurt its credibility in Egypt, he said.

“There is a state of lack of trust between the different fronts. That is a result of the U.S. administration largely supporting the tyranny of the Mubarak regime for a long time,” Shater said. “Egypt’s relations with the U.S. must be strong and strategic based on economic cooperation and all other forms of cooperation.”

Shater distanced himself from a resolution passed in parliament that demanded the revision of the peace treaty with Israel and the ouster of the Israeli ambassador from Egypt. He said all treaties would be respected but are open for revision. “We also support the Palestinian people in their current strife and in the state of injustice they are under in the shadow of the Arab-Israeli conflict and especially what is known as the Gaza siege,” he said.

Shater acknowledged that becoming president at such a difficult time could compromise the party’s popularity. He said his first priority would be to jump-start the economy by bolstering security and encouraging investment, adding that the party has been in touch with “American, European and Asian countries” to discuss economic cooperation.