Vienna - Austrian Chancellor Alfred Gusenbauer is facing severe pressure from his coalition partner after his party changed course on its European Union policy and now wants to hold public referenda for future European Union treaties.

In an unusual attempt to improve low confidence ratings, the social democratic chancellor announced his change of heart by sending an open letter to Austria's biggest newspaper.

Future European treaties, or an amended Lisbon treaty that needs a new ratification by Austria, would face a popular vote, the letter published on Thursday evening in the Kronen Zeitung said.

The conservative People's Party, the social democrats' coalition partner in government, reacted angrily to the announced change of course and said it would put the future of the coalition up for discussion.

On Friday, conservative Vice Chancellor Wilhelm Molterer demanded a meeting of both parties, in order to discuss the "basis for further cooperation," Austrian news agency APA reported.

Austrians have the most critical stance towards the EU among member states, a poll published by the EU in June shows. Austria ratified the Lisbon treaty without a referendum in April.

Gusenbauer has reacted to his lack of popularity by announcing last week that he would step down as party chief in autumn. In the meantime, he installed Transportation Minister Werner Faymann as interim and future head of the social democrats.

Political commentators expect that Gusenbauer will not keep his post as chancellor much longer either, as he faces increasing criticism from his own party officials.

In an interview with Kurier newspaper published Friday, the powerful social democratic Vienna mayor Michael Haeupl said that Gusenbauer's candidature as chancellor in the next elections "is not decided yet."

The Austrian chancellor has admitted in the past days that his party had not succeeded in effectively communicating its government policies, such as pension or education reforms. He is also under pressure from his own party, where trade unionists want him to show a stronger social democratic profile in government. (dpa)