WASHINGTON - Weaving together strands of pomp, policy, and summitry, President Obama's weeklong European tour will be all about tending to old friends in the Western alliance and securing their help with daunting challenges, from the upheaval in the Mideast and North Africa to the war in Afghanistan.

Obama's eighth trip to Europe as president, with a quick-moving itinerary - four countries in six days - unfolds against the backdrop of the NATO-led bombing campaign in Libya and economic weakness on both sides of the Atlantic.

A priority for the president and his allies will be to more clearly define the West's role in promoting stability and democracy in the Arab world without being overly meddlesome and within tight financial limitations.

Obama, set to depart late Sunday, will visit Ireland, England, France, and Poland. Each is weathering an economic downturn that has forced European nations to adopt strict austerity measures. The United States has pushed its national debt to the limit, and Obama and congressional Republicans are in contentious talks about how steeply to cut spending.

A highlight of Obama's opening stop in Ireland will be a pilgrimage to the hamlet of Moneygall, where America's first black president will explore his Irish roots.

It turns out that Falmouth Kearney, who immigrated to the United States in 1850 at age 19, is Obama's great-great-great-grandfather on his Kansas-born mother's side.

Michael Collins, the Irish ambassador to the United States, said the president's visit would be "a golden moment" for a country that's been on the economic ropes after a boom time. The visit is sure to play well at home for Obama as he heads into reelection season after being pushed to prove he was born on U.S. soil.

After his day in Ireland, Obama will spend two in England, where he and Michelle Obama will be treated to all the pomp and pageantry the monarchy can muster for the president's first European state visit.

In private, Obama and British Prime Minister David Cameron will plunge into the details of a host of challenges: Afghanistan, Libya, counterterrorism, the global economy, and more.

Both leaders then scoot to a French summit of the Group of Eight industrialized nations, where the president hopes to build on momentum from his speech days ago about how best to promote stability and democracy in the Middle East.