VIENNA (Reuters) - Austria s new conservative-far right ruling coalition is likely to be sworn in on Dec. 20, an informed source said on Friday, marking a victory for nationalists so far shut out of government elsewhere in western Europe. Foreign Minister Sebastian Kurz, whose mainstream conservative People s Party (OVP) won a parliamentary election on Oct. 15 but not a majority, has been in coalition talks with Heinz-Christian Strache s Freedom Party (FPO). Both sides have described the discussions as friendly and constructive but so far failed to disclose the kind of sweeping tax, immigration and administrative reforms they had called for in their campaigns. Kurz, 31, who has taken a tough stance on immigration and Muslim  parallel societies , tilting towards the FPO line as the far right surged in popularity, is tipped to become chancellor and the youngest head of government in the European Union. There has been no confirmation on who might get which portfolio in the new cabinet, but the anti-immigration FPO has said it would aim for about half of the ministries. The OVP gained 31.5 percent and the FPO 26 percent of votes in the Alpine republic s October election.  (Dec. 20) is certainly a possible date (for the swearing-in),  OVP Chairwoman Elisabeth Koestinger said on Oe1 radio, adding they would put quality before speed even if that meant a deal only after Christmas. FPO deputy leader Norbert Hofer told Oe1 that no deal had been sealed yet, repeating previous statements that both parties aimed to finish before Christmas. The Austrian national news agency APA also cited Dec. 20 as the most likely date for the swearing-in of the new government by President Alexander Van der Bellen, but listed Jan. 8 as an alternative date. The FPO, which came within a whisker of winning the 2015 presidential election, is allied with France s National Front and Germany s AfD, which in a September election became the third strongest party in Germany s parliament. The populist far right last entered an Austrian federal government in 2000 and currently rules in coalition with centrists in two of the country s provinces. 