Barack Obama and family will spend 24 hours in Ghana
Barack Obama is in Ghana on his first visit to sub-Saharan Africa since becoming US president.
Ghana was chosen because of its democratic track record and Mr Obama is expected to use the trip to promote good governance across the continent.
He will hold talks with President John Atta Mills and address the country's parliament on the subject of democracy.
He is due to visit a former slave fort and a health centre in the capital, Accra, as part of his 24-hour visit.
The BBC's Will Ross says President Obama will find it a challenge in the current economic climate to match some of the achievements of his predecessor, George W Bush, when it comes to health care in Africa, especially in the fight against HIV.
The visit to the slave fort at Cape Coast Castle will be a poignant moment for the country's first African-American president and for his wife Michelle, whose ancestors are believed to have come from West Africa, our correspondent says.
Andrew Harding reports on the Obamas' arrival in Accra
Posters of Barack and Michelle Obama are to be seen throughout Accra, where their arrival was eagerly awaited.
The dead can be buried later but Obama is here for once and we must pay all attention to him
Ama Benyiwaa Doe Ghanaian minister, explaining suspension of funerals in Cape Coast
On arrival, President Obama and his family were met by President Atta Mills, and treated to a colourful welcome featuring drummers and traditional dancers.
Ghanaian musicians have written songs to mark the visit and it is clear that millions of Ghanaians would love to see Mr Obama, our correspondent says.
However, there will be few opportunities for them to do so during his 24-hour stay.
When former President Bill Clinton came more than a decade ago, he addressed hundreds of thousands of cheering Ghanaians.
But post-9/11, security is tighter and all events are for invited guests only, our correspondent notes.
Key rings and umbrellas
Barack Obama visited sub-Saharan Africa while a US senator, making a trip to Kenya - his father's homeland - in August 2006.
Martin Plaut, BBC News
For Ghanaians, there is little doubt that they deserve to be Mr Obama's first real African destination since assuming office.
Nigeria was not really suitable, given the question marks over the way in which President Umaru Yar'Adua was elected. Kenya, home of Mr Obama's father, experienced post-election violence. Ethiopia has jailed the leader of the opposition, and South Africa's Jacob Zuma is new in the post and something of an unknown quantity.
Not only is Ghana clearly democratic, but it has some of the African oil on which the US increasingly depends, and there is the symbolic link with slavery, from which so many African-Americans trace their heritage.
So Ghana ticks Mr Obama's boxes - a suitable stage on which to launch the president's Africa policy on the continent itself.
Mr Obama's official business on Saturday includes talks with Ghana's president and a speech to parliament.
Ahead of the president's arrival late on Friday, people were already out celebrating, dancing and drumming in the seaside city's streets.
Memorabilia being sold by vendors ranged from key rings and coffee mugs to handkerchiefs and umbrellas bearing portraits of Mr Obama and Mr Atta-Mills.
Thousands of police have been deployed for the visit and a number of city roads were closed on Friday.
Cape Coast, a town about 160km (100 miles) west of Accra, has even suspended funerals on account of Mr Obama's impending visit to its old slave fort.
"We banned all funeral activities in Cape Coast because we want to give a befitting welcome to the US president," Ghana's central regional minister, Ama Benyiwaa Doe, told AFP news agency.
"The dead can be buried later but Obama is here for once and we must pay all attention to him."
Squeeze on aid
Obama-print dresses are on sale in Accra
Across the African continent, people are pinning a lot of hope on Barack Obama partly because of his African roots but also because of his election slogan, Yes We Can, our correspondent reports.
He arrived in Ghana hours after leaders of the G8 industrialised countries pledged billions of dollars to boost agriculture - the main source of income for many sub-Saharan Africans.
But the financial climate is different from when former President Bush was in office and American-funded programmes, such as the provision of medicine for people living with HIV, are facing new challenges.
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.