The Swiss ambassador to the United Nations, Jenö Staehelin, says only the Security Council has the authority to authorise an attack on Iraq.
Staehelin was addressing the UN highest decision-making body on Thursday during a two-day open debate by non-aligned nations on Iraq.
The ambassador said that Switzerland, a member of the UN since September, would support a two-phase approach to the Iraq question.
He said that UN weapons inspectors should first be allowed into Iraq to report on whether Baghdad is complying with its obligations concerning weapons of mass destruction.
If their information revealed that this was not the case, only then should the Security Council "take all necessary steps in complete knowledge of the facts".
Staehelin said Iraq should unconditionally accept the wishes of the UN inspectors and that presidential sites should not be subject to restrictions during inspections.
He added that action should only be envisaged after all other peaceful methods had been tried. According to Staehelin, the consequences of such action, particularly for civilians, would have to be examined first.
For Switzerland, the main goal should be the complete destruction of all illegal arms, said Staehelin. But he also stressed that the United Nations charter should be respected.
The ambassador announced that Switzerland had told UNMOVIC, the UN body in charge of weapons inspections in Iraq, that it would be ready to actively participate in the inspections.
Staehelin did not go into detail about the nature of such support but earlier this month the defence ministry confirmed that the UN had asked for eight infrastructure specialists, including plumbers, a structural engineer, electricians and air conditioning specialists.
Switzerland's ambassador to the UN praised the United States president George W Bush for softening his position on the use of force against Iraq in his bid to win the approval of the Security Council.
Iraq's decision to accept the demands of the international community was also seen favourably by Staehelin.
The position taken by Staehelin largely echoed that of foreign minister, Joseph Deiss, in a speech made to the UN three days after Switzerland joined the world body on September 10.
New US draft
Meanwhile, faced with almost unanimous opposition to a tough UN resolution authorising military action against Iraq, the United States prepared on Thursday to circulate a new plan to win the support of key Security Council members.
The new US draft gives more credence to reports from the UN weapons inspectors and shows a willingness to drop the use of troops for the opening any routes barred during inspections.
But diplomats say the draft plan still authorises the use of force, which may hinder its acceptance in the Security Council.
France and Russia, two of the permanent members of the Council, said they were keen to resolve the issue and get weapons inspectors back into Iraq.
But neither said whether they would be willing to approve a plan that allows Washington to use force if Baghdad fails to meet UN requirements.
swissinfo with agencies
Switzerland says that there can be no action against Iraq without UN security council backing.
It favours a two-phase approach to Iraq, first letting weapons inspectors in and then discussing action if Iraq does not comply.
Switzerland has offered infrastructure support to the UN weapons inspectors.
The Swiss welcome Washington's new stance on Iraq.