The U.S. embassy in Burma has announced the arrival of Washington's first ambassador to the country in 22 years.

The embassy in Rangoon said Ambassador Derek Mitchell arrived Wednesday and would travel to Naypyitaw to present his credentials to President Thein Sein. Mitchell previously served as special envoy to Burma.

Also Wednesday, the Obama administration announced it is easing restrictions on U.S. companies interested in doing business in Burma. A White House statement said easing such sanctions will provide “immediate incentives” for reformers and benefit the Burmese people.

But the statement also warns that the United States remains “deeply concerned” about the lack of transparency in Burma's investment environment and the military's role in the economy. It says existing sanctions authorities have been expanded to include those who undermine the reform process, engage in human rights abuses, contribute to ethnic conflict, or participate in military trade with North Korea.

The United States has been re-engaging Burma after a new, nominally civilian government took over in March of last year and began implementing reforms.