United Nations Special Envoy Noeleen Heyzer.

Noeleen Heyzer "will focus on addressing the deteriorating situation and immediate concerns as well as other priority areas of her mandate," according to a UN statement issued late Monday.

It did not give details on who she would meet among the junta's top leadership or whether she would seek to meet Suu Kyi.

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On Monday Suu Kyi received another prison term in a secretive junta court, taking her total jail time to 17 years.

A statement from the junta confirmed Heyzer's trip would begin on Tuesday but did not provide further details.

Heyzer is expected to hold meetings in the military-built capital Naypyidaw, according to a diplomatic source who did not give further details.

Myanmar's ousted civilian leader Aung San Suu Kyi speaks during a meeting. File photo

Diplomatic efforts to resolve the crisis led by the UN and the Association of Southeast Asian Nations regional bloc have made little headway, with the generals refusing to engage with opponents.

The generals had "repeatedly disregarded calls by ASEAN leaders for concrete and inclusive dialogue for national reconciliation," Malaysia's foreign minister said on Tuesday.

Last month the junta stoked renewed international condemnation when it executed Phyo Zeya Thaw, a former lawmaker from Suu Kyi's National League for Democracy party, for offences under anti-terrorism laws.

In response, the UN Security Council -- including junta allies Russia and China -- issued a rare condemnation of the junta.

Singaporean sociologist Heyzer was appointed by UN Secretary-General Antonio Guterres last year, replacing Swiss diplomat Christine Schraner Burgener.

Schraner Burgener had called for the UN to take "very strong measures" against the military and had been the target of regular broadsides in Myanmar's state-backed media.

Since the coup, the Swiss diplomat had been blocked by the generals from visiting the country, where she had hoped to meet with Suu Kyi.

In December state media reported the junta had closed her office in the country "since the activities of Ms Christine Schraner Burgener have concluded".

It has not yet said whether it will allow Heyzer to open an office.

Agence France-Presse