The Muslim Brotherhood will be a part of the committee tasked with drafting Egypt's interim constitution.
The group's appointment to the eight-member panel suggests the military may be willing to legitimize the Brotherhood nearly 60 years after it was banned.
The panel's legal expert says radical changes are not planned and restrictions on freedoms will be removed.
The new constitution, which is expected to be drawn up in 10 days, will be in place until democratic rule is established. After elections are held, the military will transfer power to the new government.
"The future parliament and government can decide whether to make further amendments or rewrite the whole thing," committee member Mohammed Hassanein Abdel-Al said.
Meanwhile, the Brotherhood announced Tuesday that they would form a political party.
"The Muslim Brotherhood group believes in the freedom of the formation of political parties. They are eager to have a political party," spokesman Mohammed Mursi said in a statement on the Brotherhood website.
Still, the group promised they would not run any candidate for the upcoming presidential elections, saying such a move would be too controversial.
"We are not going to have a candidate for the upcoming presidential elections," Essam el-Arian, a prominent Brotherhood member, said. "It's time for solidarity. It's time for unity. In my opinion, we need a national consensus."