Her Majesty Queen Elizabeth, Head of the Commonwealth, has warned of the threat of climate change to "smaller, more vulnerable" Commonwealth nations in a historic speech to the UN General Assembly this week.

Speaking at the organisation's headquarters in New York on 6 July 2010 for only the second time in 53 years, the Queen congratulated the United Nations on its "remarkable" achievements in tackling humanitarian emergencies, reducing conflict and helping to alleviate poverty.

"For over six decades the United Nations has helped to shape the international response to global dangers," the Queen remarked as she echoed her call at the Commonwealth Heads of Government Meeting in Trinidad and Tobago late last year for states to show "leadership" in the face of challenges such as peace and development.

She said: "New challenges have also emerged which have tested this organisation as much as its member states. One such is the struggle against terrorism. Another challenge is climate change, where careful account must be taken of the risks facing smaller, more vulnerable nations, many of them from the Commonwealth."

During her speech, the Queen also noted that since she last spoke at the UN the world has witnessed positive changes in science and technology as well as social attitudes.

The Queen added that the Commonwealth lent its "whole-hearted support" to UN efforts to reduce conflict and procure peace around the world.

"Since I addressed you last, the Commonwealth, too, has grown vigorously to become a group of nations representing nearly two billion people. It gives its whole-hearted support to the significant contributions to the peace and stability of the world made by the United Nations and its Agencies," she said.

"Last November, when I opened the Commonwealth Heads of Government Meeting in Trinidad and Tobago, I told the delegates that the Commonwealth had the opportunity to lead. Today I offer you the same message."

The Queen was speaking at the United Nations for the first time since 1957. In addition to her role as Head of the Commonwealth, she is also Queen of 16 United Nations member states including the United Kingdom.

She continued: "It has perhaps always been the case that the waging of peace is the hardest form of leadership of all. I know of no single formula for success, but over the years I have observed that some attributes of leadership are universal, and are often about finding ways of encouraging people to combine their efforts, their talents, their insights, their enthusiasm and their inspiration, to work together."

A symbolic role, the Head of the Commonwealth holds discussions with Commonwealth leaders in national capitals in London and during Heads of Government Meetings. She visits the host country during each summit, meeting the leaders in individual audience and at larger formal functions.