Thein Sein, Myanmar's president, has held a landmark talks with one of the country's biggest ethnic rebel groups.

Delegates from the Karen National Union (KNU) met Sein in the capital Naypyidaw on Saturday, following negotiations with ministers in Yangon on Friday.

The meeting was the first time the president, who issued a call for dialogue last August, aimed at bringing them into Myanmar's new political system, had met with the rebel leaders.

"The president explained his change of attitude towards ethnic armed groups," a mediator, who participated in the meeting and wished to remain anonymous, told the Reuters news agency by telephone.

An independent member of the peace negotiation group present at the talks, who asked not to be named, described the encounter as "warm and open".

"The KNU said they will continue peace talks with the government until the end. They said they would urge other ethnic groups to work for peace," he said.

Six delegates, including members of the armed wing of the group, were taken "by special flight" for the landmark meeting, which lasted about 90 minutes, officials said.

Sein, a former commander and heavyweight in the military governement that ceded power a year ago, told the KNU delegation that his government viewed the rebels as brothers rather than an enemy.

Wave of reforms

The mediator also said that Sein, 66, had indicated the constitution could be amended to give all groups political representation.

"The weapons held in their hands should not be for fighting each other but for defending the country," he quoted Sein as telling the KNU.

The KNU's armed wing has been battling the government since 1949, one year after the country then known as Burma became independent in 1948.

Myanmar's government signed a ceasefire deal with the group in January

The peace process is one of the most ambitious plans by the current quasi-civilian government dominated by retired generals.

The new administration has embarked on a wave of social, political and economic reforms that it says are "irreversible" as it seeks to get sanctions lifted to allow a flood of foreign investment into one of Asia's last remaining frontier markets.

The West had slapped sanctions on the former government, which was accused of the suppression of ethnic minorities and human rights violations by its troops.

Peace with the rebels has been demanded by Western nations now reviewing economic and political sanctions.

Sein's meeting comes after an historic by-election on Sunday won by the opposition leader Aung San Suu Kyi's League for Democracy Party.