CAIRO – Egypt’s Islamist and secular forces sought to relaunch the street uprising against Egypt’s ruling military Friday. Tens of thousands of protesters packed Cairo’s Tahrir Square in the biggest rally in months, accusing the generals of manipulating upcoming presidential elections to preserve their power.

But attempts by protest organizers to form a united front against the military were blocked by competing agendas. The protest was riven by distrust and resentments that have grown between Islamists and liberals during the rocky, military-run transition process since the fall of President Hosni Mubarak more than a year ago.

Liberals and leftists accuse the Muslim Brotherhood of abandoning the “revolution” months ago and allying with the military in hopes of securing power.

At Friday’s rally, many said the Brotherhood was only turning to the streets after the generals proved more powerful in decision-making even after an Islamist-dominated parliament was elected. The liberal groups warned that the Brotherhood could accommodate the military again for a chance to govern.

“The Brotherhood are here for the throne, that’s all. We tried them before and they rode the revolution and the blood of martyrs,” said Mohammed Abu-Lazeed, an accountant who took part in a march to Tahrir led by communists and socialists.

The Brotherhood said it was protesting to preserve the revolution.

The elections set to begin May 23 were intended to be a landmark in Egypt’s transition: the first free choosing of a president after decades of authoritarian rule. After the president is installed, the military is to hand over by the end of June the power it took after Mubarak’s ouster.

Instead, political chaos in the lead-up to the vote has fueled fears that the military aims to push a candidate it favors into the presidency in order to continue its influence and block reform.

This week, the election commission disqualified 10 candidates, including the top three contenders. The move enraged Islamists because among those excluded were the Brotherhood’s nominee and a favorite of ultraconservatives known as Salafis.