United Nations efforts to secure the release of 21 peacekeepers abducted in the Golan dragged on into a third day on Friday as Manila said rebels holding the Filipinos were sticking to their demand that Syrian troops leave the area.

UN peacekeeping chief Herve Ladsous was to brief the Security Council on the abduction later on Friday as concern mounted about its implications for the future of the four-decade-old UN force patrolling the sensitive armistice line between Israel and Syria.

The refusal by the Syrian rebels to compromise had dampened hopes of a swift release and forced Manila to step up its negotiation efforts, Philippine Foreign Affairs Spokesman Raul Hernandez said.

The 21 Filipinos - members of the UN Disengagement Observer Force monitoring the armistice between Syria and Israel that followed the 1973 Arab-Israeli war - were abducted by the rebels on Wednesday just one and a half km to the Syrian side of the ceasefire line.

The rebels are demanding that Syrian troops move 20 km back from Jamla, an area at the southern end of the armistice zone, Hernandez said. "The demand of the rebels for the repositioning of Syrian forces in the area of Jamla is still outstanding so this is still being worked out," he said on ABS-CBN television.

The Philippine government had previously received information that raised hopes the 21 would be released on Friday morning, Philippine time, and the government now did not know if or when they would be freed, Hernandez said. "We are trying to intensify our negotiations with the rebel groups."

However, he said the Philippine peacekeepers were still being treated well.