YANGON, Myanmar (AP) — The first U.S ambassador to Myanmar in 22 years formally assumed his job last month by presenting his credentials to the country’s president.

Derek Mitchell carried out the formality at the presidential mansion in the capital of Naypyitaw, according to the website of the office of President Thein Sein. Mitchell had arrived in Yangon, the country’s biggest city, before proceeding to the capital.

Mitchell previously was U.S. President Barack Obama’s special envoy to the country. The U.S. Senate confirmed his appointment as ambassador in late June.

Washington announced in January it was restoring full diplomatic relations with Myanmar, encouraged by reforms that have swept the nation since a long-ruling army junta ceded power last year.

Thein Sein, who took office after a general election, has instituted liberal reforms after almost five decades of repressive military rule. The initiative in large part is meant to attract foreign aid and investment. The previous military regime was shunned by many western countries, who applied economic and political sanctions because of its poor record on human rights and democracy.

Prior to Mitchell’s arrival, the highest level American diplomat in Myanmar was the charge d’affaires.