Syria has said any attempt to deliver humanitarian aid to rebel-controlled areas without government approval is tantamount to "an attack on the state" as well as its territorial integrity and political independence.
The country's United Nations ambassador Bashar Ja'afari sent a letter to the world body's secretary general Ban Ki-moon and the UN Security Council from Syrian and Arab lawyers protesting against a draft council resolution that would authorise the delivery of humanitarian aid into Syria through four border crossings without approval from President Bashar Assad's government.
Currently, all UN aid must go through Damascus - a practice which UN humanitarian chief Valerie Amos has repeatedly criticised.
Key council members have been negotiating the text of the draft - initially circulated by Australia, Luxembourg, and Jordan - for several weeks.
Australia's UN ambassador Gary Quinlan has said 90% of aid currently "goes to government-held areas" and Syrians in opposition-controlled zones are not getting food and medicine.
Authorising humanitarian access at two crossings from Turkey, one from Jordan and one from Iraq would help more than two million people who have not received aid, he said.
But the lawyers sharply disagreed.
"The sole purpose of the initiative is to use United Nations auspices for the delivery of logistical backing to the terrorists, in preparation for the establishment of 'humanitarian corridors' under the protection of those very states that brought terrorism on to Syrian national territory," they said.
The Syrian government calls all opposition groups and al Qaida-linked extremists "terrorists".
The letter, obtained by The Associated Press, said all humanitarian aid must be delivered with the agreement of the government.
"Importing aid in co-ordination with terrorist organisations and without consultation with the Syrian state would amount to an attack on the Syrian state and on its territorial integrity and political independence," the lawyers said.
"Not only would it violate the (United Nations) charter, it would use the charter as a pretext for aggression."
The resolution was initially drafted under Chapter 7 of the UN Charter, which means it could be enforced militarily, but that was dropped at the insistence of Russia, Syria's most important ally.
Russia's UN ambassador Vitaly Churkin said Moscow came up with "an elegant, innovative formula" that would allow humanitarian supplies to go through the four crossing points "which will simplify the humanitarian procedures when the goods are actually on the territory of Syria".
He said Western members of the council had been examining the draft since Tuesday and expressed hope that the resolution would be adopted quickly.
"Frankly, my suspicion is that their main interest very often ... (is) to produce some kind of a political big bang," Mr Churkin said. "When the political big bang is not there, when in fact we focus on the humanitarian situation, then quite often they'll lose interest in the entire exercise. So we'll see what comes out of this discussion on the resolution."
Mr Quinlan said on Thursday that the latest revised Russian draft "is not good enough and can take us backwards potentially".
"We need to make sure it works on the ground and generates greater access, but we are not convinced it is the case," he said.
All 15 council members voted for a resolution in February demanding that all sides in the Syrian conflict allow immediate access for aid. UN officials have said the resolution has failed to change the dire humanitarian situation.
Meanwhile Mr Ban says the humanitarian situation in Syria is worsening and the number of people needing urgent help has now reached 10.8 million - almost half of Syria's population of 22 million.
Mr Ban's monthly report to the Security Council said the current estimate of 3.5 million people living in areas that are difficult or impossible for humanitarian workers to reach was also likely to have increased to 4.7 million people.
"Efforts to expand humanitarian assistance to those most in need have been met with continued delays and obstruction," he said.
The UN chief also reported severe levels of violence including intensified use of barrel bombs by government forces against civilian areas, and suicide attacks, reported executions and other acts of terrorism by extremist groups.