Leading European members of the North Atlantic alliance warned the US at the weekend that Nato could not become a global policeman, but must be used by both sides as a political forum to debate and agree on significant security issues such as Iran, the Middle East and energy security.

Angela Merkel, Germany’s new chancellor, led the European calls for continuing reform of the organisation, with a plea to expand its political scope to co-ordinate strategy between Europe and the US outside the Nato area.