Berlin  - The upper house of the German parliament was voting Friday on the Treaty of Lisbon and was expected to pass the European Union's reform accord by considerably more than the two-thirds majority required.

The vote in the Bundesrat, which represents the governments of the 16 states, is the final legislative hurdle facing the treaty, which then goes to President Horst Koehler for signature.

Some legislators, from the socialist Left Party in particular, have signalled they could mount a constitutional challenge to the treaty through the courts after the Bundesrat vote.

Last month, the lower house passed the treaty by 514 votes for to 58 against, with one abstention. The 53 members of the Left made up the bulk of the opposition.

Chancellor Angela Merkel, who was one of the main drivers of the process leading up to the slimmed down treaty, described it as "good for Europe" and a "win for Germany."

The treaty was signed in the Portuguese capital on December 13. It replaces the failed European constitution, which was abandoned after the French and Dutch rejected it in referenda in 2005.

The 27 EU member states are being asked to ratify the treaty by the end of the year, ahead of elections to the European Parliament in 2009. Ireland is to hold a referendum on the treaty in June - the only country to do so.

The treaty, a complex legal document comprising a string of amendments to previous EU deals, aims to streamline decision-making through increased use of majority votes and creates the offices of an EU president and foreign policy supremo with clout. (dpa)