British Foreign Secretary Philip Hammond said on Wednesday he was not optimistic that world powers and Iran would clinch a full nuclear deal by Nov. 24 but that there may be a way of extending the self-imposed deadline.
"I'm not optimistic that we can get everything done by Monday," Hammond told reporters in the Latvian capital.
"But I think if we make some significant movement we may be able to find a way of extending the deadline to allow us to get to the final deal if we're making a good progress in the right direction."
In an attempt to end the 12-year dispute over Iran's nuclear program and dispel fears of a new Middle East war, six world powers and Iran are negotiating a settlement they hope can be reached by Monday.
They aim to reach a comprehensive settlement at talks in Vienna that would curb Iran's atomic activities in return for a phasing out of sanctions that have severely hurt its oil-dependent economy.
Iranian and Western officials have said the deadline is unlikely to be met and that an extension is the most likely outcome. They say it is possible to agree the outline of a future accord, but it would take months to work out the details.
"We do very much want to see a deal done with Iran, but we don't want to do a bad deal. Better then no deal than a bad deal," Hammond said.
"The right deal with Iran has to be one which gives us the assurance we need that Iran's program is exclusively targeted at civil nuclear use, has no military dimension at all and where Iran's enriched capacity is limited to a level which does not present any military threat," he said.
Hammond said Iranian negotiators would have to show "considerable further flexibility" over the next four days to get a deal.
The six states -- France, China, Russia, Germany, the United States and Britain -- want Iran to scale back its capacity to refine uranium so that it would take much longer to produce fissile material for a bomb if it wanted to.
Tehran says it is enriching uranium only to make fuel for nuclear power plants and that this is its sovereign right.
