The three-month-long standoff between Egypt's ruling Supreme Council of the Armed Forces (SCAF) and the Muslim Brotherhood's Freedom and Justice Party (FJP) reached a crescendo on Tuesday. The SCAF threatened that, unless agreement could be reached among political forces – including the FJP – on the formation of a constituent assembly, tasked with drafting a new constitution, by 2pm Thursday, the SCAF would move to do it unilaterally.

On Tuesday, a six-hour meeting between the SCAF and representatives of 19 political forces wrapped up with a unanimous agreement that formation of the constituent assembly could not wait any longer. A committee, including representatives of the Nour, Wafd and Free Egyptians parties, was put in charge of contacting the FJP and the Islamist Al-Wasat Party, both of which boycotted Tuesday's meeting.

"Thursday's meeting will be decisive and [SCAF head] Field Marshal Hussein Tantawi's message was clear to all: unless a 100-member constitution-drafting assembly is in place by Thursday at 2PM, the military council itself will form it," said independent MP Mostafa Bakri.

Most observers expect that, if agreement is not reached, the SCAF will move to amend Article 60 of last year's constitutional declaration. This article gives the two houses of parliament – the People's Assembly and Shura Council – the authority to draw up the assembly. "The article will be amended so as to give the SCAF the right to form the assembly in accordance with the guidelines adopted at the 28 April meeting with all political forces," said Bakri.

The 28 April meeting between the SCAF and party representatives ended in a six-point deal

According to the deal, the assembly will include 37 party representatives and 63 public figures. The latter will include four representatives of Al-Azhar; six Coptic, Catholic and Anglican representatives; ten professors of constitutional law; four representatives of the main judicial authorities; and four representatives of workers and farmers. The 63-member list would also include representatives of student organisations, women and the handicapped.

In addition to the amendment to Article 60, there is a general expectation that the SCAF would also issue an 'addendum' to last year's constitutional declaration, laying down the prerogatives and duties of Egypt's new president until a new constitution can be drafted.

On Monday, the SCAF met with its advisory council to debate the issue. Advisory council head Sameh Ashour explained that "in light of fears that a new president will be elected and the transitional period completed without a new constitution, the advisory council proposed that the SCAF move to amend Article 60 and issue an addendum to the constitutional declaration on the powers and duties of the new president."

The SCAF's move appears to have met with the support of prominent constitutional law professors and secular forces.

Ahmed Kamal Abul-Magd, a constitutional law professor and a member of the advisory council, said that "the SCAF is fully empowered to amend Article 60 of the constitutional declaration, in the event that Parliament fails to form a constituent assembly."

"Parliament has complete legislative powers, but does not have the right to issue or amend constitutions," argued Abul-Magd.

Hassanein Abdel-Al, another prominent constitutional law professor, agrees with Abul-Magd, arguing that "the People's Assembly's legislative powers do not include issuing or amending constitutions. These are the prerogative of the head of the state."

Secular forces – liberal and leftist parties – agree that the SCAF made the move on Tuesday in order to end the stalemate that came about when Islamist parties that won parliamentary elections blocked participation in the constituent assembly by minority parties. This triggered a boycott of the constitution-drafting process by liberal and secular forces, which charged that the Muslim Brotherhood had exploited its FJP-led majority in Parliament to impose control over the constituent assembly and ensure that the constitution reflects its own religious convictions.

Mohamed Abul-Ghar, chairman of the Egyptian Social Democratic Party, which boycotted Tuesday's meeting, argued that "the Islamist-dominated Parliament deliberately delayed the formation of the constituent assembly for its own political ends."

Abul-Ghar continued: "After several meetings with the FJP, most political parties came to the conclusion that the group has a long record of broken promises and can never be trusted to form a constituent assembly."

Abul-Ghar and others believe that the Brotherhood delayed the 28 April deal on the constituent assembly, opting to wait and see if its presidential candidate – Mohamed Morsi – would win or lose the first-round presidential vote. "If Morsi won, the constitution would be tailored to give the president sweeping powers; if he lost, it would be drafted to grant parliament tremendous powers," said Abul-Ghar.

Abul-Ghar pointed out that the Brotherhood had backtracked after the SCAF's meeting with political forces, which had reached an agreement on 28 April on a set of guidelines for forming the constituent assembly.

It is a fact that Parliament Speaker Saad El-Katatni, the FJP's former secretary-general, refused to endorse the 28 April deal and asked Parliament's legislative affairs committee to set up a new constituent assembly. The meetings of this committee, however, were boycotted by most political parties and finally reached a deadlock. The committee opted to issue a report containing vague guidelines on the formation of the constituent assembly, but this was never discussed in Parliament.

The SCAF's move was sharply attacked by the Brotherhood's FJP. Brotherhood leaders gave no clear-cut reasons for their decision to boycott the meeting with SCAF on Tuesday. They merely said: "This is not the right time to hold such a meeting."

El-Katatni, however, warned on Tuesday that any attempt by the SCAF to issue an addendum to last year's constitutional declaration or amend any of its articles – especially Article 60 – would represent an infringement on Parliament's exclusive legislative authority. "Everyone should know that since 23 January – when the People's Assembly met for the first time – the power of legislation has been the exclusive right of parliament, and nobody else has the authority to issue any laws, decrees or constitutional declarations," El-Katatni said.

He added: "I want to clearly state that Parliament will never allow anyone to usurp its exclusive rights.”

After the meeting with the SCAF on Tuesday, Bakri said: "The SCAF is determined that, unless agreement is reached among political forces within 48 hours, it would move to unilaterally amend Article 60 of the constitutional declaration so as to adopt the guidelines reached on 28 April," adding that this would not constitute "a meddling with the prerogatives of the People's Assembly."

Bakri went on to cite the SCAF's legal advisor, Major-General Mamdouh Shahin, as saying that the SCAF was "completely entitled to amend Article 60 or issue a constitutional addendum without putting the matter up for debate in the People's Assembly or in a public referendum."

Bakri also cited Shahin as saying that if political forces could reach an accord on the formation of a constituent assembly, outlining the framework of the new constitution, and delineating the prerogatives of the elected president, there would be no need for unilateral action by the SCAF in this regard. Otherwise, however, the SCAF will be forced to amend Article 60 unilaterally and issue an addendum to the constitutional declaration.

Chairman of the liberal Wafd party El-Sayed El-Badawi, for his part, expressed optimism, saying, “I think that all political parties will be able to reach an agreement on the 28 April guidelines.

In their meeting with the SCAF, political parties also rejected the notion of forming a presidential council, stressing that ongoing presidential elections must be allowed to run their course.