Britain's Queen Elizabeth II appealed to Commonwealth leaders Saturday to strive to embrace reform and bridge cultural differences to meet new challenges and counter terrorism.

As she opened the 35th Commonwealth Heads of Government Meeting (CHOGM) here, the queen also made a strong plea for greater racial and religious tolerance saying it was its diversity that made the 54-nation group relevant in the 21st century.

But she added: "The Commonwealth must move with the times if it is to remain relevant to all generations."

Dressed for a colourful ceremony in flame-red with a matching

hat, the queen also used her speech to underline the need for a continuing effort to reach consensus in a summit which looks set to be overshadowed by differences over Zimbabwe.

She told the 900 guests, including the leaders of 35 governments, the Commonwealth, established in 1931, was an organisation which had defined its own values and ideals through its particular focus on issues important to it, notably sustainable development and good governance.

"It has also developed its own style of informality, tolerance and an insistence on bringing all along together on the sometimes difficult path of building consensus."

This tradition of consensus was in spite of the remarkable variety of

its membership with every region of the world represented, every size of nation at all stages of development and all the great religions.

"I also believe it is this very diversity which makes the Commonwealth so increasingly relevant in our 21st century world," she said.

"The events of 11th September have reminded us all of the need to build bridges between different cultures based on greater knowledge and understanding of our differences."

Few of the countries of the Commonwealth were homogenous and most had different traditions and cultures, she said.

"National success can often be judged by the success with which we deal with difference."