UK ministers have set out a series of "red lines" they say they will not allowed to be crossed in negotiations over the new European constitution. The government says the UK is ready to veto the whole project if it does not get its way on these key issues.
The "red lines" were outlined in a white paper earlier this year:
Defence: The UK says it must remain in control of its own defence and foreign policy. There must be no European defence cooperation which undermines or replaces Nato (the Atlantic alliance headed by the US which includes most of Europe).
Treaty changes: The UK says it opposes the removal of the national veto for major decisions on the EU's future.
Tax: Taxation must be decided by nation states alone. The draft constitution would allow for majority voting on measures to tackle cross border tax fraud - British ministers think this would allow the EU into the tax field by the back door.
Justice: The UK says it is determined to stop majority voting being introduced for steps towards harmonising European common law systems. It also insists it will not give up the UK's right to carry out frontier patrols.
Social Security: The British argument here is that social support systems are very complicated and so the EU should only be allowed to make changes through unanimous votes.
European resources: The UK wants any changes to the EU's right to raise certain funds to be agreed by unanimity alone. That would protect the controversial British annual budget rebate, secured by Margaret Thatcher in the 1980s.