Mexico City, Sep 8 (IANS): The Mexican government could unveil a key infrastructure investment plan as early as September 15 that includes private sector participation in energy and communications projects, President Andres Manuel Lopez Obrador said. "We have already made significant headway. It's just a matter of reaching an agreement (as to when) so that the plan is presented here," Xinhua news agency quoted the President as saying at a briefing on Monday.