KATHMANDU (AFP) - Nepal's Maoist chief apologised Wednesday for his party's role in a parliament brawl that injured four security officers in the tense run-up to a deadline for a post-war constitution.

Maoist lawmakers hurled chairs and scuffled with security staff early Tuesday as ruling party politicians tried to push proposals for a new charter through parliament before Thursday's deadline.

"The confrontation in the constituent assembly meeting on Tuesday morning was a mistake," said Maoist leader Pushpa Kamal Dahal, known better as Prachanda.

"We had no intention of starting a fight, but the situation got out of control," Prachanda told a press conference.

He said the party had instructed lawmakers to disrupt proceedings by chanting slogans, but matters got out of hand when ruling party politicians attempted to move ahead with a vote on terms of the constitution.

The former rebels say discussions should continue until all parties agree - even if that means missing the deadline to approve the charter and complete a peace process begun in 2006, when they ended their decade-long insurgency.

Disagreements persist on crucial issues, with the opposition calling for new provinces to be created along lines that could favour historically marginalised communities such as the Madhesi and Limbu ethnic minorities.

Other parties say such a move would be divisive and a threat to national unity.

The ruling parties and their allies have the two-thirds majority in parliament that they need to approve a constitution without Maoist support.

But the former insurgents have warned of further conflict if the parties fail to take opposition views into account.

The Himalayan nation has endured political limbo since 2006 with no agreement on the new charter and growing disillusionment among ordinary Nepalis frustrated over the long delay.

Lawmakers are widely expected to miss Thursday's cut-off, with parliament adjourned until Wednesday afternoon after the opposition obstructed the morning session.