President Obama welcomed Nigerian President Muhammadu Buhari to the White House on Monday, and praised his country for undergoing a peaceful transition of power.

"Nigeria is obviously one of the most important countries in the world and one of the most important countries in the African continent," Obama told reporters, with Buhari and top administration officials gathered together in the Oval Office. "Recently, we saw an election in which a peaceful transition to a new government took place.  And it was an affirmation of Nigeria’s commitment to democracy, a recognition that although Nigeria is a big country and a diverse country with many different parts, nevertheless the people of Nigeria understand that only through a peaceful political process can change take place."

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Buhari, who served as a military dictator in Nigeria in the 1980s after his faction helped oust a democratic regime from power, won the presidency in late March in what was widely regarded as a free and fair election. President Goodluck Jonathan willingly transferred power to his successor, marking the first democratic transition from the ruling party to the opposition since the continent's most populous nation ended military rule in 1991.

Shortly after Buhari's visit, Obama will depart for Kenya and Ethiopia. Some human rights advocates and foreign policy experts have questioned why Obama chose to visit Ethiopia, whose May elections failed to yield a single opposition seat in parliament, rather than Nigeria on that trip.

[Editorial: Mr. Obama’s visit to Ethiopia sends the wrong message on democracy]

Grant Harris, senior director for Africa at the National Security Council, said Friday that the administration took the "unprecedented action" of inviting Buhari to the United States rather than have Obama visit Buhari in the Nigerian capital of Abuja because it gives the new president access to many more top American policymakers.

"And our view was that we needed to have this occur as soon as possible, and that we would also want to maximize this opportunity to have him in Washington with his advisers," Harris said, adding that Cabinet officials, such as Treasury Secretary Jacob J. Lew and Attorney General Loretta Lynch, will have a chance to confer with Buhari. "Whereas they might not otherwise or would not be traveling on this trip that the president has coming up. It’s an opportunity for President Buhari and his team also to meet with members of Congress, and to meet with civil society and non-governmental organizations here and speak to a domestic audience."

Buhari, who said he was "extremely grateful" for the invitation, noted the "positive trends" of elections in his country and credited "pressure from the United States and Europe to make sure elections were free and credible" for leading them to where they are now.

Vice President Biden, National Security Adviser Susan Rice and Secretary of State John F. Kerry all joined Buhari and Obama in the Oval Office Monday morning.

"It’s a reset of the bilateral relations, which is what both sides have wanted for several months," said American University professor Carl LeVan, author of the book  “Dictators and Democracy in African Development: The Political Economy of Good Governance in Nigeria.

LeVan added that the administration clearly views Buhari's recent reform moves, such as the decision to replace the heads of Nigeria’s army, navy and air force, as "credible and meaningful."

[READ: Buhari on the push for good governance and fight against terrorism, in his own words]

"President Buhari comes into office with a reputation of integrity and a very clear agenda and that is to make sure that he is bringing safety and security and peace to this country," Obama said, noting Buhari was committed to curbing the spread of the Islamic militant group Boko Haram. "And he has a very clear agenda with respect to rooting out the corruption that has too often held back the economic growth and prosperity of his country."

"On both these issues, we’re looking forward to hearing more about his plans and how the United States can partner with Nigeria so that Nigeria ends up being an anchor not only of prosperity and stability in the eastern part of the continent, but can also be an outstanding role model for developing countries around the world," Obama added.