Washington - Barack Obama will make a first presidential pilgrimage to his father's homeland of Kenya this week, the capstone of a weeklong overture to Africa taking in three key nations.On Monday, Obama will host recently elected Muhammadu Buhari, the president of Nigeria - Africa's most populous nation and biggest economy - at the White House.On Thursday, he will jet to Nairobi, and from there trace the Great Rift Valley northward to Addis Ababa, becoming the first US president to visit Ethiopia.The first African-American president of the United States has visited his ancestral continent four times while in office, but has not yet traveled to Kenya during his White House tenure.The father Obama has admitted he had "never truly known," was born in Kenya's far west, in a village near the equator and the shores of Lake Victoria.A pipe-smoking economist, he walked out when Obama was just two and died in a car crash in Nairobi in 1982, aged 46.Obama's planned "homecoming" was long delayed by Kenyan President Uhuru Kenyatta's indictment for war crimes by the International Criminal Court.Those charges, linked to ethnic violence, were suspended last year - in part, prosecutors say, because the Kenyan government thwarted the investigation.SymbolicBut the suspension has paved the way for the landmark visit and a meeting between the two men."It's obviously symbolically important, and my hope is that we can deliver a message that the US is a strong partner, not just for Kenya, but for sub-Saharan Africa," Obama said ahead of the trip.Trade and security are expected to dominate political discussions. But there will also be a personal and symbolic flavor, even down to the meeting with Kenyatta.Obama's father was an economist in the government of Kenyatta's father Jomo, who led Kenya at independence from Britain until his death 14 years later in 1978.The two men did not get on well, with Kenyatta senior sacking Obama senior, and blackballing him for further government jobs, an ostracization that would help fuel alcoholism.The two presidents will put that aside, as Obama tries to make his mark in Africa.Obama has sometimes struggled to burnish his legacy on the continent, as the "Great Recession," crises in the Middle East, terrorism and a "pivot to Asia" have all sucked up time and effort."This trip is extraordinarily important for the president," said former US assistant secretary of state for Africa Johnnie Carson."It's an opportunity to build upon and consolidate his legacy with respect to Africa."Diplomatic sources say a debate is raging inside the White House about whether that legacy may include playing a role in solving the conflict in civil war-torn South Sudan.Tens of thousands of people have died and over two million people have been forced to flee their homes in the nation founded in 2011.But there are many risks to Obama's deeper involvement, both on the ground and with regard his political standing should he fail.'Africa rising'On his first presidential trip to Africa, in 2009, Obama gave a speech in Ghana that spoke to a "new moment of promise" on the rapidly rising continent.But the rise has been curbed by security problems, as well also corruption and rights abuses, issues that are sure to come up in Nairobi and Addis Ababa.Kenya has been hit by a string of attacks. In 1998, al-Qaeda-linked militants blew up the US embassies in Nairobi and Dar es Salaam, killing hundreds.In April this year, Al-Qaeda-affiliated Shebab rebels massacred 148 people at Garissa University, most of them students."Since Kenya is on the frontlines of the fight against terrorism, the US is providing equipment and training for our security forces," said Kenyan ambassador to the United States Robinson Njeru Githae.Also in Kenya, Obama will attend a Global Entrepreneurship Summit, aimed at promoting businesses that promise to lift many more Africans out of poverty and help insulate societies against radicalization.In Addis Ababa, Obama is expected to address leaders of the African Union, remarks that are likely to touch on Africa's democratic deficit.More than 50 African and global human rights groups - including Human Rights Watch and Freedom House - have written to Obama to take a democratic message to Africa.The charges against Kenyatta, and the fact Ethiopia's government won 100% of parliamentary seats in a recent disputed election, has raised questions about whether Obama should go at all.