Non-government groups complained Tuesday that they have been excluded from international talks on a conventional arms treaty that have now entered a second week.

Under pressure from a small group of countries, the treaty conference has decided to exclude "civil society" groups from half the negotiation sessions, Oxfam arms control expert Anna MacDonald told reporters.

"We are concerned that the shady secretive world of arms dealing seems to become the shady secret world of negotiations too, behind closed doors.

"These are the states that we heard being quite vociferous in their arguments against the meeting moving on," the expert said naming Algeria, Cuba, Egypt, Iran, North Korea, Syria and Venezuela.

Activists from around the world have come to New York for the nearly four weeks of talks at the UN headquarters.

The 193 UN members have until July 27 to hammer out a deal for a treaty on the conventional weapons trade, which experts estimate to be worth more than $70 billion a year.

States have spent seven years preparing for the talks, which officially started on July 3 after being held up over a dispute on the representation of the Palestinians and the Vatican.

They have since been slowed by countries who oppose a legally binding treaty, according to diplomats and activist groups.

In a speech to the conference on Tuesday, Iran's UN ambassador Mohammad Khazaee said the talks should only deal with arms trafficking and should exclude missiles, light arms and munitions. Governments must have the "right" to defend themselves, he said.

European nations generally want a binding treaty but the United States wants munitions excluded, saying they are too difficult to control. Russia and China also have objections.

UN leader Ban Ki-moon has demanded strict standards for arms exports and national legislation, though he acknowledged that "the global arms trade touches on core national interests."

The United States is by far the world's biggest arms trader, accounting for more than 40 percent of conventional weapons sales. Britain, China, France, Germany and Russia follow.