The United Nations said on Monday it would wait for the results of US, NATO and Afghan investigations into a deadly air strike on a Medecins Sans Frontieres (MSF) hospital in Afghanistan before deciding whether to support an independent probe.UN Secretary-General Ban Ki-moon on Saturday called for an "impartial" investigation of the incident but he stopped short of saying that should be done by the UN His spokesman Stephane Dujarric said on Monday it was too soon to say if an additional probe would be necessary. MSF and the UN human rights chief have said the incident could be a war crime."It's still early days, I think we're waiting to see what comes out of the official US and NATO and possibly Afghan investigations," he told reporters. "I think what we're looking for is a credible and transparent investigation."US Defense Secretary Ash Carter has promised a full investigation into whether the American military was connected to the destruction of the MSF hospital in Kunduz, but cautioned it would take time to gather information.Under international law, the bombing would only be a war crime if it was proved that the hospital was attacked intentionally, legal experts said. A United Nations investigation is unlikely at this point because the United States is viewed as capable of carrying out a credible investigation and because the incident is not viewed as part of a systematic campaign targeting civilians, diplomatic sources said. If doubts arose over the credibility of the US or NATO investigations, there might be calls for a UN probe.MSF has called for a "full transparent independent investigation." A spokesman for the group, which said it had given the coordinates of the hospital to US and Afghan forces, did not immediately respond to a query about whether it wants a UN investigation.UN human rights chief Zeid Ra'ad al-Hussein said on Saturday that, "if established as deliberate in a court of law, an air strike on a hospital may amount to a war crime."