The British attempts to win backing from undecided countries on the security council and bridge the gap between France and America had still failed to bear fruit last night.

British concessions on its "compromise" proposal met with American impatience, French and Russian intransigence, and growing scepticism from the "middle six" nations as talks were set to carry on over the weekend.

Leaked memos from the Spanish UN ambassador Inocencio Arias to his foreign minister, Ana Palacio, showed that the US had prevented Britain from watering down the proposed ultimatums to Saddam Hussein.

Mr Arias himself said Britain was becoming "nervous" and "exclusively obsessed" with domestic public opinion.

"The British effort ... is an attempt to show to their public opinion that London has made, right up until the last moment, a major effort to seek peace (which explains the leaks to the press and the determination to show that this is an individual initiative)," he wrote after Wednesday's closed door session.

The Spanish ambassador complained Britain had reneged on an agreement to keep the details secret.

"Today, just when the three co-proposers here agreed that we would not reveal any of the points ... Mr Straw's textual explanations reach me on the internet," Mr Arias complained.

Mr Arias's memos, passed to the Guardian by the Spanish Cadena Ser radio station, revealed the enormous tension behind the closed doors of the security council meeting.

Chile yesterday proposed a new plan with a three-week deadline for Saddam Hussein to meet conditions for disarming. It was rejected immediately by the White House.