DUP deputy leader Peter Robinson has told the assembly that the requirement for all major parties to be included in a Stormont executive must be temporary.
The debate is taking place at Stormont
Mr Robinson said the government system designed by the Good Friday Agreement was "fundamentally undemocratic".
He was speaking in a debate on potential changes recommended by the cross-party Preparation for Government Committee.
These include reducing the number of assembly members.
It also recommends a phasing out of the "dual mandate" under which some assembly members also serve as MPs or councillors.
Under the Good Friday Agreement any power-sharing executive must include all the major parties.
However, Mr Robinson told the debate that if the mandatory coalition was the only option, it should be temporary and must not be imposed on future generations.
UK Unionist leader Bob McCartney contrasted that statement with the DUP's last Westminster election manifesto which described such a mandatory coalition including Sinn Fein as being "out of the question".
Mr McCartney asked whether the DUP could be slightly in favour for a limited period of time of a coalition it regards as undemocratic.
Before the debate, the DUP said that further changes to the Stormont rules will be necessary if there is to be a deal on power sharing.
Devolved government was suspended over allegations of a republican spy ring.
The court case that followed collapsed and one of those involved, Denis Donaldson, later admitted working as a British agent.
Direct rule from London was restored in October 2002 and has been in place since.
The Preparation for Government Committee was set up to identify obstacles to the return of devolution. It met over the summer months.