Just how do you get the government to the table? FAR 33.214 does not require the parties to conduct ADR. But it does require the contracting officer to answer your request stating the reasons for denial which are somewhat limited. The new DFARS (and we hope a new FAR clause) should help (See In Praise of Mediation below). We certainly need strong government acquisition leadership to make ADR work.
But my favorite form of ADR is what DFARS calls "structured unassisted negotiation". What is that and how does it work? It is not in DFARS or FAR. See www.spriggsconsultingservices.com/resolve_disputes.shtml.
If that does not work, get your case to the ASBCA or CBCA as quickly as possible. File your notice of appeal from the contracting officer's decision (or deemed denial), file your complaint and ask for a settlement judge. You cannot formally without making it a joint request. However, you can ask for a status conference during which you politely invite the judge's assistance in getting the parties to the table. I assure you, the judges at these Boards love to encourage negotiated settlements.