United front from Obama and Cameron © Reuters/Dylan Martinez The Prime Minister is heading to Washington for high-profile talks with Barack Obama, with both men pledging their support for the "essential relationship" between Britain and the United States. Afghanistan is certain to dominate the agenda at the White House in the wake of the deaths of six British troops and the massacre of 16 civilians by a US soldier. The two leaders have emphasised their united front with a joint article in Tuesday's Washington Post. "The alliance between the United States and Great Britain is a partnership of the heart, bound by the history, traditions and values we share," they wrote. But what makes our relationship special - a unique and essential asset for our nations and the world - is that we join hands across so many endeavours. Put simply, we count on each other and the world counts on our alliance. Mr Cameron has said that the "dreadful" events of the past few days must not be allowed to derail the Afghan mission and he will want to hear assurances that the US is committed to the agreed strategy of gradual withdrawal by the end of 2014. The three-day visit will also see a star-studded state dinner at the White House, a trip on Air Force One to watch a basketball game in Ohio and public appearances for Samantha Cameron with First Lady Michelle Obama, in what will be seen as a celebration of the close links between Britain and the US. The warmth of trans-Altlantic relations is demonstrated by the fact that Mr Cameron is the first foreign leader to be invited by Mr Obama to fly with him on his official jet.