The United States has been supporting a campaign by the Somali government for the embargo to be ended, while Britain and France have been more reluctant to let more arms into a country already awash with guns, diplomats said.
The measure is likely to be part of a council resolution renewing the mandate of the African Union military force in Somalia which should be passed on Wednesday next week.
The Security Council imposed a total arms embargo in 1992 as feuding warlords battled for control of the country after ousting dictator Mohamed Siad Barre.
A UN diplomat said Britain is drafting the resolution which set out the new measures, but that negotiations are still being held.
The council could decide to ease the embargo against government purchases of arms for a year but exclude certain types of weaponry such as air defense systems, the diplomat said.
“There is a a good argument for sending a strong signal that the new government is increasingly exercising sovereignty, and on the other hand continuing concerns about security,” the diplomat said.
President Hassan Sheikh Mohamud, who took office last year, but is still kept in power mainly by the 17,000 strong African Union Mission in Somalia (AMISOM), toured western capitals last month to demand an end to the embargo.
“What the Somali government partly wants is a political signal that they are now a sovereign government and we’re supporting them, rather than a trusteeship,” said another UN diplomat. “They say the bad guys are getting weapons and the good guys are not.”
UN Secretary General Ban Ki-moon has also given conditional support to lifting the embargo.
“Enhanced efforts are … urgently needed to develop the Somali National Security Forces,” Ban said in a recent report to the Security Council in which he said it “may wish to consider the repeated request by the government for lifting the arms embargo.”
Ban warned that while Shebab Islamist militants have suffered major losses “these spoilers will seize any opportunity to reverse the gains.”
AMISOM’s current UN mandate ends on March 7. The Security Council is currently scheduled to meet the day before to vote a resolution on the force and setting up a UN political office in Mogadishu.