MADRID, July 15, 2008 (AFP) - Spain is set to complete the parliamentary ratification process of the European Union's Lisbon Treaty later on Tuesday with the document's expected approval in the upper house of parliament, one month after its rejection by voters in Ireland.

The Senate will gather in an 'extraordinary session' at 1 p.m. (1100 GMT) to debate and vote on the treaty, which seeks to streamline EU institutions as the bloc expands, a spokesman for the upper house of parliament told AFP.

Spain's lower house of parliament voted overwhelmingly in favour of ratifying the treaty on June 26 with 322 deputies in the 350-member chamber coming out in favour.

If the Senate approves the text as expected, it will then need to be signed by King Juan Carlos for the ratification process to be completed.

He could sign the treaty later this week, which would make Spain the 23rd EU country to ratify the document.

The treaty, which must be ratified by all 27 EU member states to take effect, was rejected by 53.4 percent of voters in Ireland in a June referendum, plunging the bloc into a new institutional crisis.

The Senate vote had originally been planned for late September or early October but the main opposition Popular Party together with the smaller Catalan nationalists CiU and Basque nationalist party PNV requested that it be held before the legislators take their summer break.

The treaty has the backing of Prime Minister Jose Luis Rodriguez Zapatero's ruling Socialist Party and the Popular Party.