Mr Gerry Adams said Sinn Fein was committed to a full and productive role in achieving a conclusive resolution to the current impasse.
But he claimed it was unacceptable to allow the Democratic Unionist Party to dictate the pace of progress.
"The decision by the governments to put off intensive negotiations until September means that they have bought into the time-frame set down by the DUP," he said.
"Once again the governments are allowing unionism to set the pace in the process. This is unacceptable."
Mr Adams said there was no reason to delay efforts to resolve the deadlock for the summer and added he would put this to the Irish and British governments at talks nest week.
The planned discussions are due to be held next Friday to review progress and assess the situation before intensive negotiations in September in a bid to restart the Belfast Assembly.
At the annual Wolfe Tone commemoration parade in Bodenstown, Co Kildare, Mr Adams said republicans had the political will to reach a comprehensive deal.
"Sinn Fein believes that it is possible to achieve a comprehensive and holistic package, which deals with all of the outstanding matters in a way that is definitive and conclusive.
"But allowing a party, which has clearly declared itself against the Good Friday Agreement and which refuses to accept and respect the mandates of others at this time should not be allowed to set the pace."
Mr Adams also attacked the Labour Party for courting a possible future coalition with Fine Gael in a bid to ensure ministerial seats.
He said Labour had made the mistake of rescuing Fine Gael from the political doldrums in the past and should now look at alternatives.
"People don't want more of the same. If Labour is interested in alternative politics it should work with others to build a real left alternative, instead of concerning itself with getting Ministerial seats."