The new Timor Gap agreement was signed today with the tensions of tough negotiations still apparent.

The document was signed by Foreign Minister Alexander Downer, Resources Minister Nick Minchin, East Timorese Economics Minister Mari Alkatiri and UN appointed American negotiator Peter Galbraith. The man expected to become East Timor's first president, Xanana Gusmao, joined the international press taking photographs of the event.

Finalised this week after a year of protracted and rocky negotiations, the deal splits revenue from the oil and gas developments in the area, with 90 per cent going to East Timor and 10 per cent to Australia.

The original Timor Gap Treaty between Australia and Indonesia was signed by foreign ministers of the two countries in an aircraft over the Timor Gap in 1989. But East Timor, at the time a province of Indonesia which had invaded the territory in 1975, had no say in the treaty.

Moments before the signing ceremony at the United Nations headquarters in Dili at 11.45am, Alkatiri said he was undecided about whether he would go through with it while Northern Territory Chief Minister Denis Burke was in the same room. Mr Alkatiri is angry with the NT government for flying an East Timorese delegation to Darwin for briefings earlier this year while negotiations were bogging down in Canberra.

A member of the East Timorese interim parliament, Angela de Freitas, interrupted the signing ceremony to declare the new agreement for sharing of Timor Gap oil and gas illegal. "Don't sell our country," she said as she was escorted from the UN Transitional Administration in East Timor (UNTAET) office by security. Mr Downer commented that it was good to see freedom of speech operating in East Timor.

Mr Galbraith said the negotiations were surprisingly difficult against negotiators who succeeded in protecting Australia's interests. "They were surprisingly difficult and I speak as one whose most recent experience was negotiating peace agreements in the Balkans," Mr Galbraith said.

"I think the result is one that both negotiation teams can take pride in," he said. Mr Downer said the agreement was one that Australia was comfortable with. It would provide security for developers of the Timor Sea resources.

"It is an agreement that will encourage oil and gas companies not only to continue with the projects that already exist but also in the future to explore and develop other projects," Mr Downer said.

"This is a fair agreement, this is a just agreement, this is an agreement with a true basis in international law." Mr Alkatiri said it would be up to a democratically elected government of East Timor to agree to a new treaty.

But while not binding to a future East Timor government, Mr Galbraith said it provided investors with more surety than the 1989 treaty with Indonesia that its replaced.

"Let me tell you it provides a hell of a lot better certainty than they [energy companies] had under a treaty with Indonesia in which they were in effect making investment in stolen property," Mr Galbraith said.