Douglas Alexander, the newly-appointed International Development Secretary, will fly the British flag in Washington today as he argues for development and trade to be at the centre of any foreign policy.

Mr Alexander, speaking to the Council on Foreign Relations in Washington, will set out the Brown government's political imperatives, including a commitment to tackle poverty and climate change, and help for fragile states with support for rebuilding international institutions.

He will say: "In the 20th century a country's might was too often measured in what they could destroy. In the 21st century strength should be measured by what we can build together."

He will add: "And so we must form new alliances, based on common values, ones not just to protect us from the world but ones which reach out to the world. A new alliance of opportunity."

Mr Alexander will acknowledge, and indeed praise, the special relationship and the UK's closeness to the United States but he will also challenge the international community, including America, to establish new policies and priorities to face the new challenges.

He will say: "National interests can be best advanced and protected through collective action.

"We need a global community able to act together through modern effective institutions, including a reformed UN, IMF, World Bank, WTO and EU.

"We must reiterate our responsibility to act to address the big challenges of our time - poverty, human rights abuse, climate change and genocide.

"It can be right, when certain conditions are met, to intervene in the affairs of countries to prevent genocide, crimes against humanity, humanitarian suffering or threats to democracy.

"We believe that our collective responsibility to protect individuals transcends the right of nations to absolute sovereignty."