A senior Sudanese opposition figure said on Sunday her party has been invited to meet government officials this month to discuss a national dialogue aimed at resolving multiple crises.

President Omar al-Bashir, who is wanted on war crimes charges, launched the dialogue in October to try to resolve the insurgencies in Sudan's border regions and the country's faltering economy.

READ: Will Bashir talks lead to fair elections in Sudan?

Most opposition groups refused to join the process, demanding a meeting outside Sudan to agree to its terms.

But Umma party deputy head Mariam al-Mahdi told AFP her party had been invited by the African Union for a meeting this month in Addis Ababa.

"We will definitely take part in that meeting and we are very much grateful for the African Union Higher Implementation Panel," the body planning on mediating the talks, Ms Mahdi said.

The Umma party, led by her father Sadiq al-Mahdi, is one of Sudan's oldest political institutions.

Sadiq al-Mahdi has lived abroad since August 2014, when he signed an agreement to work together to solve the country's crises with an alliance of rebels from the Darfur, Blue Nile and South Kordofan states.

Mariam was detained by Sudanese security forces for a month because of those talks.

She said her party received the invitation to the meeting in Addis Ababa last week and that it was due to take place in January.

"We hope to get out of a brief time — two to three days — the rules and procedures of the national dialogue," Ms Mahdi said.

Counter-insurgency

The meeting could pave the way for the Umma to join the dialogue but it is unclear whether President Bashir's ruling National Congress Party will attend, as it shunned similar negotiations in March.

Ms Mahdi said if the meeting was successful, her father could return to Sudan soon afterwards.

It was unclear which other groups had been invited, and the African Union did not immediately comment.

President Bashir, who ousted Mr Sadiq al-Mahdi in a 1989 military coup, announced the dialogue in January 2014 and it was initially well received by his opponents.

But his insistence on holding national elections last April before the dialogue started won him much criticism, with some saying the talks were intended as a distraction before the vote.

Despite poor turnout and international criticism of the ballots, President Bashir was re-elected with more than 94 per cent of the vote.

The Sudanese is wanted by the International Criminal Court for alleged war crimes and crimes against humanity during the bloody counter-insurgency he unleashed in the western Darfur region, roiled by conflict since 2003.

He announced a two-month ceasefire in September, extending it by one month in a speech on new year's eve.