Talks in Geneva which started on Monday and were originally scheduled to end on Tuesday ground on into Wednesday afternoon as negotiators tried to overcome objections by Syria, which traded jibes with Israel about who was to blame.
The impasse led Switzerland, the depositary state for the conventions, to change its mind regarding a consensus decision and threatened to call a rare vote to break the deadlock.
Swiss Ambassador Blaise Godet warned delegates in a closed-door session that a vote could be the only way out as proposed by Chile in an attempt to narrow differences.
The new "red crystal" emblem would join the Red Cross and Red Crescent and ease the way for Israel's Magen David Adom (MDA - Red Star of David) organisation to become part of the international emergency service and humanitarian network.
The MDA is officially unrecognised in the Geneva Conventions, signed by 192 countries including Israel, because its emblem does not conform with longstanding rules allowing only a cross or a crescent.
Abdul Rahman Attar, head of the Syrian Red Crescent, told journalists his country was still demanding an agreement on humanitarian aid in the Israeli-occupied Golan heights as a condition for approving the new emblem.
Syria says Israel is neglecting the health needs of the 25,000 Syrian citizens who live in the Golan, which Israel annexed in 1981.
"It's definitely not good for the humanitarian movement. Decisions have always been taken by consensus"
Mohammad Reza Alborzi,
Attar claimed the MDA only gives "selective" treatment to Syrians who are prepared to accept Israeli rule in the Golan.
Syria is demanding the creation of a hospital there run by Syrian residents of the Golan but supervised by the International Committee of the Red Cross.
But Israeli ambassador Itzhak Levanon dismissed the Syrian position.
"We have been very forthcoming, we have been very flexible and pragmatic in order that this conference will be a success," Levanon told reporters.
"We have a very large, substantial majority. There is only one country, Syria, which is blocking all these efforts. So we are trying our best," he said.
He also questioned the need for a Syrian-run hospital in Golan and rejected claims that the MDA denies treatment to those who need it.
If no agreement is reached a two-thirds majority can still change the rules.
Attar, head of the Syrian Red
Crescent, in a press conference
But negotiators were trying to avoid having to go to a vote, said Iran's ambassador Mohammad Reza Alborzi.
"It's definitely not good for the humanitarian movement. Decisions have always been taken by consensus. There is a hope that that criterion will be maintained," Alborzi said.
"We are trying to bridge differences so we don't have to come to a vote," said Pakistan's envoy Masood Khan, whose country currently serves as president of the Organisation of the Islamic Conference (OIC).
If it came to a vote among the 140 delegations present from the 192 who have signed the conventions, the outcome was uncertain as representatives of many countries have indicated they have no voting instructions.
If the rules are changed, the MDA would be able to use the crystal outside Israeli territory, including during international disaster relief operations.
Ending one longstanding stumbling block, the MDA and the Palestinian Red Crescent last week signed a landmark accord that amounted to formal political recognition between them.