Hopes of a pre-election deal in Northern Ireland have been dashed, Downing Street has admitted.

In a surprise statement Number 10 expressed its regret at last night's breakdown in talks over power sharing in the province.

The prime minister's office admitted it had "not proved possible" to bring unionists and republicans together.

The intervention came after David Trimble said his party would not resume its position in the Stormont executive.

"The outstanding issue is the degree of transparency to be attached to acts of decommissioning," said the Downing Street statement.

"Despite the lengthy and constructive engagement of the leadership of the Ulster Unionists, the government regrets that it was not possible to reach agreement on these matters in terms which were conducive to creating public confidence on all side."

Number 10 confirmed that elections would still go ahead on November 26.

But it refused to say whether the assembly would then subsequently meet or whether devolution would be restored.

"Elections will take place on November 26, as announced last week. After that the British and Irish governments will work with the parties to resolve the issue as quickly as possible, so as to enable devolved government to be restored to the people of Northern Ireland," said the statement.

"We remain optimistic that this will be achievable, building on the progress we have made in the last week."

All parties would have to commit to the "fundamental principles" of the Good Friday agreement, the statement added.

"The continuing implementation of the agreement also remains a firm commitment and that's why we shall seek after the elections urgently to create the conditions which will enable a working executive to be formed and all the elements of the joint declaration to be taken forward," added the statement.

In a sign it hopes pro-agreement parties will poll well, Number 10 said it hoped next month's poll would be "positive and constructive".