U.S. President Barack Obama began his two-day state visit to Britain on Tuesday, aimed at ensuring the U.S. and Britain keep the special nature of their relationship.

United States remains our most important ally, and our two nations contribute to the security and prosperity of our peoples and of the world through shared national interests, Queen Elizabeth of the United Kingdom said during a welcome dinner, commenting on the ties between the two countries, a White House statement said.

Our alliance is a commitment that speaks to who we are, Obama said at the dinner hosted by the Queen at Buckingham Palace in London.

Obama and Britain's Prime Minister David Cameron are to announce the formation of a U.S.-British national security council to work together on international challenges and share intelligence, an Obama administration official said.

Review of NATO action to help end conflict in Libya and Western policy towards uprisings in the Arab world, is also one of the agendas of the president's UK visit.

Obama, who visited Ireland before UK, is on a four-nation European tour to Ireland, England, France and Poland, along with first lady Michelle Obama.

The president and his wife was treated to royal pomp at Buckingham Palace, where they dressed royally for the dinner - Obama made it cordial with Prince Phillip in a mid-twentieth century style tailcoat reaching below his knees, and Michelle dazzled in an immaculately white gown with criss-cross V-neck, gloves and a matching clutch.

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