The Freedom and Justice Party (FJP) and other political parties met with the Supreme Council of the Armed Forces (SCAF) at 2.30pm on Thursday to discuss the formation of Egypt's constituent assembly.
The meeting is still underway at the time of writing.
The meeting came after political parties reached a consensus in the early hours of Thursday morning regarding the formation of the constitution-drafting assembly.
The Muslim Brotherhood's FJP had announced earlier on Thursday that it would not attend the meeting with the SCAF as it had not been invited.
"Only the parties that attended the first meeting with the SCAF [on Tuesday] were invited [to Thursday's meeting]," said the FJP's Essam El-Erian.
The party boycotted Tuesday's meeting, stating that the constituent assembly should be formed without interference from the SCAF.
However, after a meeting of the FJP's executive board early Thursday, the party decided to attend the meeting.
An FJP statement said the agreement reached at Wednesday's meeting of political parties showed "everyone is keen to put Egypt's interests above their own, and that the patriotic political groups in Egypt are capable of reaching a consensus and overcoming any disagreement."
The SCAF stated Tuesday that if no consensus was reached between political parties on the criteria for forming the constituent assembly, it would either issue an amended version of the March 2011 Constitutional Declaration or revive the 1971 Constitution.
The Egyptian Bloc, which includes the liberal Free Egyptians Party, the Social Democratic Party, and the leftist Tagammu Party, did not hide its discontent with the agreement reached by political parties on the constituent assembly, saying that there was more to the formation of the assembly than dividing the membership between different groups.
After hours of wrangling at the meeting that began Wednesday and ended at 4am Thursday, the parties agreed that 39 of the 100 seats on the constituent assembly would be given to political parties, of which the Muslim Brotherhood's Freedom and Justice Party (FJP) would hold 16; the Salafist Nour Party eight; the liberal Wafd Party five; the Free Egyptians Party two; the Egyptian Social Democratic Party two; and one each for the moderate-Islamist Wasat Party, the Nasserist Karama Party, the Socialist Popular Alliance Party, the liberal Reform and Development Party and the Islamist Building and Development Party.
Mohamed Abul-Ghar, head of the Egyptian Social Democratic Party and Egyptian Bloc MPs Emad Gad and Farid Zahran walked out of the meeting as they felt the FJP parliamentarians would take over the assembly. Free Egyptians Party representatives also withdrew from the meeting.