The coordinator said that work on Article 16 has improved the text considerably, in the view of a wide range of delegations. Still, he added, there is "some question as to whether this procedural step needs to be in the statute (at all) ... The main concern on the text is the right of challenge given to non-state parties without any corollary obligations on their part."

Added to that challenge, Holmes added, text that was previously considered closed following discussions in New York is being re-opened here - a process the working group coordinator finds legitimate, but genuinely cumbersome.

"There have been issues that people thought were resolved during the preparatory committee meetings (in New York) that were re-opened here," Holmes said, noting particularly Article 15, the basic language on the admissibility of ICC cases.

"Obviously, in principle, this is a draft statute: Everything is open for discussion," Holmes said. "But from a practical point of view, given all that we have to do, the hope is that things that were agreed to in preparatory committees, in a wide-open format in which all nations could participate, would not have to be re-examined here."

Several human-rights groups worry in particular about changes suggested by Mexico to Article 15, which they contended could rip apart the delicate balance throughout the statute on language about complementarity between national jurisdictions and that of the ICC. "Opening that language now could force all the previous compromises on complementarity to fall apart," one NGO official said.

Still, one rights activist said, Mexico's actual proposals were "not as bad as we had expected".  In one revision, Mexico wanted a change from language suggesting that the ICC could investigate cases where "there has been an undue delay" in national proceedings to one in which there is "an unjustified delay". In another, ICC investigations justified by the "partial" collapse of a country's judicial system would be replaced by those in the event of a "significant" collapse.

Holmes said that his working group is looking closely at the article to see whether it can accommodate "some small changes to the text that don't upset the overall balance", so that the previous agreements on complementarity can stay in place.