Ashraf Ghani Ahmadzai was sworn in as president of Afghanistan on Monday in the first transfer of power in that country since the removal of the Taliban.

After taking the oath, Ghani Ahmadzai swore in presidential challenger Abdullah Abdullah as chief executive, fulfilling a campaign promise to share power, according to a report from Associated Press.

The appointment of Abdullah is likely to calm tensions between the country's north and southeast regions. There had been threats of violence if Ghani Ahmadzai had not held to his word.

Ghani Ahmadzai also could be a positive for U.S.-Afghani relations, according to John Podesta, a senior advisor in administration of U.S. President Barack Obama.

The change in power will likely lead to the signing of a security pact on Tuesday that would allow U.S. troops to stay in the country beyond the end of the year, Podesta said.

U.S. Ambassador James Cunningham will sign the agreement on Tuesday, and it's unclear if Ghani Ahmadzai or a lower member of government would sign the deal on the Afghan side.

The deal will allow about 10,000 American troops to stay in the country after the U.S.-led mission ends on Dec. 31, The Los Angeles Times reported.

Former Afghan President Hamid Karzai had refused to sign the deal despite U.S. threats of a full withdrawal in the absence of legal protections for American forces. Officials have said that the delay in the deal's signing does not affect plans for next year.

In his first speech before the country, Ghani Ahmadzai asked the Taliban and other militants to lay down their weapons and join the Afghan politics. The same day, militant violence in Afghanistan killed at least 12 civilians and police officers.

"We are tired of war," Ghani Ahmadzai said. "Our message is peace, (but) this doesn't mean we are weak."

Chief Executive Abdullah, a former foreign minister, spoke before the new president and commended the Afghan people for voting despite threats from Taliban militants.

"We are committed as one in the national unity government," Abdullah said. "Our commitment will be fulfilled together as unified team to create national unity."