US Secretary of State Hillary Clinton has arrived in Senegal’s capital Dakar, as she begins an African tour.
Security issues are expected to dominate the trip, which comes just months after Islamist militants seized parts of neighbouring Mali.
Mrs Clinton is also likely to praise Senegal’s democratic achievements after recent elections.
Her 11-day tour will also take her to South Sudan, Uganda, Kenya, Malawi, South Africa and Ghana.
Mrs Clinton’s visit comes at a time of growing threats in the Sahel region, where the US military is playing an increasingly important role, says the BBC’s Thomas Fessy in Dakar.
Security issues are expected to feature in discussions between Mrs Clinton and Senegalese President Macky Sall.
The US Africa Command, or Africom, has been pumping considerable resources into training forces throughout West Africa.
Mrs Clinton is also expected, in a public address, to hail the country as a democratic example in a region plagued by conflicts and coups.
In March elections, Mr Sall defeated Abdoulaye Wade, who had been in power since 2000 and whose bid for a third term led to deadly protests.
While acknowledging the solid democratic fundamentals that Senegal has built since independence in 1960, the US had repeatedly warned the previous administration about rampant corruption, our correspondent says.
On Friday, Mrs Clinton will travel to South Sudan, becoming the most senior US official to visit the country since it became independent last year.
The tour also includes a private meeting with South Africa’s anti-apartheid leader Nelson Mandela, now 94, in his hometown of Qunu.
Her last stop will be Ghana, where she will attend the 10 August state funeral for the country’s late president, John Atta Mills, who died last week.