The sanctions extension comes days after a visit to Myanmar by Kurt Campbell, the assistant US secretary of state responsible for East Asia and the Pacific.
During the visit last week Campbell held talks with senior government ministers in the administrative capital, Naypyidaw, during which he warned the military against buying weapons from North Korea, calling on the country to abide by UN sanctions prohibiting such transactions.
His comments appeared to be Washington's strongest warning yet amid fears that the military government is seeking to acquire nuclear technology from North Korea.
|Aung San Suu Kyi briefly met Kurt Campbell in Yangon during his visit [AFP]
The extension of US sanctions also comes after the opposition National League for Democracy (NLD), led by Nobel peace laureate Aung San Suu Kyi, was forcibly dissolved after refusing to meet a May 6 deadline to re-register as a political party - a move that would have forced it to expel its own leader.
The dissolution was mandated under widely criticised laws governing the elections, which are expected to take place later this year although no firm date has yet been announced.
Under the election laws unveiled in March, anyone serving a prison term is banned from being a member of a political party and parties that fail to obey the rule will be abolished.
The government has kept Aung San Suu Kyi under house arrest for nearly 20 years.
She led her party to a landslide victory in Myanmar's last elections in 1990 but the result was never recognised by the military.
Campbell, who held talks with Aung San Suu Kyi during his visit to Myanmar last week, said later that the US was "profoundly disappointed" at the preparations for the upcoming elections.
He called on Myanmar's government to take "immediate steps" to address fears that the vote would lack legitimacy.