In reply to dave_59:
Dave, you said that the interface signals would have to be declared as ports. Would a modport work instead?
interface dut_internal_if;
logic a;
logic b;
modport dut_mp (
input a,
input b
);
endinterface: dut_internal_if
bind dut:dut_iii dut_internal_if.dut_mp if_iii (.a(a),.b(b));