(BRUSSELS) - British Prime Minister Gordon Brown said Friday that Britain could not definitively ratify the EU's Lisbon Treaty until a court has ruled on the validity of the move following a legal challenge.

"Ratification will not take place of course until we have had the judgement from the judge," Brown told journalists on the sidelines of an EU summit in Brussels focused on the treaty.

Earlier a judge at London's High Court called on the British government to delay its ratification of the embattled EU reform treaty until he rules on a legal bid to force a referendum.

Brown said that the court's ruling was expected next week and that the final steps between the treaty receiving royal assent and final ratification would also take some time.

"We actually wrote to the court saying we were proceeding to ratify so that they had the knowledge that we are taking the steps, which of course take days and in some cases weeks between the royal assent and the ratification," he said.

"The judge has now replied that he expects to give his judgement next week and of course that fits in with our timetable," given "all the different procedures before ratification".

The Lisbon Treaty bill was given royal assent on Thursday after being approved by parliament. The absolute final step in the ratification process comes when Britain deposits its "instruments of ratification" in Rome.

After the Lisbon bill gained royal assent, a Foreign Office spokesman said London planned to deposit its instruments of ratification in Rome "within weeks".

The process involves Rome because technically the Lisbon Treaty -- which was rejected by Irish voters last week, plunging to EU into a fresh crisis -- is an amendment to the Rome Treaty which founded the European bloc.

The Lisbon Treaty, aimed at streamlining the European Union as it enlarges to the east, has already had a significant setback when Irish voters rejected it at a referendum last week.

The EU leaders, who ended two days of talks in Brussels, also struggled to avert another problem by assuaging the Czech Republic that it's own judicial process concerning the treaty could continue before ratification.

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