Yangon  - A high-level US delegation visiting Myanmar on an "exploratory" diplomatic mission this week failed to meet with representatives of the pro-junta National Unity Party (NUP), state media reported Friday.

US Assistant Secretary of State Kurt Campbell and his deputy in charge of South-East Asian affairs Scot Marciel visited Myanmar on Tuesday and Wednesday on what they called an "exploratory mission" to explain the Washington's new policy of engagement towards the country's pariah regime.

The delegation, however, failed to engage with representatives of the NUP and other pro-junta parties, according to state media reports.

"Although arrangements have been made for Mr Kurt [Campbell] to meet with central executive committee members of [the] National Unity Party at its headquarters and representatives of the remaining officially registered political parties at the hotel where he put up, he did not meet them," The New Light of Myanmar reported.

"Instead, he separately met some persons who are still being scrutinized at the residence of charge d' affairs of [the] US embassy on their own arrangements," the government mouthpiece said.

One NUP executive complained that they waiting all day for Campbell to show up.

In Bangkok on Thursday, Marciel acknowledged that the USA's new policy of engaging with the notoriously uncooperative Myanmar junta was unlikely to bear swift results.

"We're going in to this with our eyes wide open," Marciel said. "Success is far from guaranteed."

Past diplomatic efforts to persuade Myanmar's generals to mend their dictatorial ways, either through sanctions as imposed by the US and the European Union, or through the tact of "constructive engagement" as pursued by Asian governments, have failed.

The country has been under military rule since 1962, and has kept opposition leader and pro-democracy icon Aung San Suu Kyi under house detention for 14 of the past 20 years.

Campbell and Marciel met with Myanmar Prime Minister Thein Sein, Suu Kyi and numerous other government and opposition leaders on their two-day visit. It as not immediately clear why they gave the NUP leaders a miss. (dpa)