UNITED NATIONS, Sept 3: UN Secretary General Ban Ki-moon has said the use of force is only legal when it is in self-defence or with Security Council authorisation.

He was replying to a question at a press briefing on Tuesday about legality of any attack on Syria. His statement appeared to question the legality of US plans to strike Syria without UN backing. On Monday, two Republican Senators backed President Obama’s case to attack Syria for its use of chemical weapons against his own people.

”The use of force is lawful only when in exercise of self-defence in accordance with Article 51 of the United Nations charter and/or when the Security Council approves of such action,” Ban said.

“That is a firm principle of the United Nations.”

Obama had said on Saturday he was “comfortable going forward” without the approval of a United Nations Security Council, so far has been completely paralysed and unwilling to hold Assad accountable.