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.

Obama and Britain's Prime Minister David Cameron are expected 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.

Obama and David Cameron on Wednesday will stress a united effort to pressure Libyan leader Muammar Gaddafi to step down, while glossing over differences between their two governments.

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 United Kingdom, is on a four-nation European tour to Ireland, England, France and Poland, along with first lady Michelle Obama.

The president and his wife were treated to royal pomp at Buckingham Palace, where they dressed in royal attire for the dinner.

On May 25, Obama with first lady Michelle Obama and David Cameron with Samantha Cameron served lunch to U.S. and British military service members, veterans and family members in a courtyard at 10 Downing Street in London.

Take a glimpse of Obama with first lady Michelle Obama and David Cameron with Samantha Cameron serving lunch:

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