NEW YORK (AP) — U.N. humanitarian aid delivery from Turkey to rebel-held northwestern Syria is tightly monitored and remains critical, Secretary-General Antonio Guterres says in a report that could be key to keeping the effort going. Syria, which isn’t a council member, called the cross-border convoys politicized and unnecessary. U.N. officials, the United States, Europeans and others said the cross-border deliveries remained crucial, warning that stopping them could bring devastating consequences for a million or more Syrians. Hence the new report, in which Guterres details how cross-border shipments are checked and tracked. “The cross-border operation remains an essential part of the humanitarian response and will continue to do so as long as needs cannot be addressed at the same scope and scale through any other modality,” he wrote.