By UN correspondent Mark Devenport

The United Nations administrator for East Timor, Sergio Vieira de Mello, says he has received assurances from Jakarta that the militia groups still active in Indonesian-controlled West Timor, will be disarmed and disbanded.

In a briefing to the UN Security Council, Mr Vieira de Mello also argued that swift injections of cash to East Timor were essential to stave off widespread social unrest in the territory.

In his first briefing to the Security Council since he took over as head of the UN administration in East Timor, Mr Vieira de Mello warned that pro-Indonesian militias behind last year's rampage of violence, still posed a threat in the territory's border areas.

The UN special representative said that in recent weeks, there had been eight cross-border incursions by the militias into the enclave of Acusi, which is entirely surrounded by Indonesia and West Timor.

Mr Vieira de Mello said the UN peacekeepers, who are this month taking over from the Australian-led intervention force, would deter or repel any further threats with firmness and he appealed to council members for their continuing support.

He said: "East Timor will rely upon your assistance to ensure that the recent harassment of East Timor borders will not be allowed to continue.

"Pro-autonomy groups and political militias in West Timor accept the outcome of the popular consultation and opt for a moderate democratic course of action.

"The remaining extremist groups and militias in West Timor should be disarmed and disbanded once and for all.

"I have discussed this once again with the government in Jakarta last week and have been given assurances that this will happen."

Dealing with the economy of East Timor, Mr Vieira de Mello pointed out that 80% of the population are without any visible means of support.

He said that projects to re-build the territory's infrastructure would make a tangible impact but would not be implemented for some months.

The UN administrator says this gap in time could create a perception amongst the East Timorese people that little is being done to help them - so large cash advances will be essential in the short term to prevent social unrest.