The document published by the two parties on Saturday outlines the demographic situation, economic development, the sustainability of the pension system, climate change and the shift towards a highly skilled labour force as the country's biggest challenges.

A prerequisite for this is that Estonia continues solidly as a European and democratic state based on the rule of law. Discrimination on the basis of ethnicity, race, skin colour, gender, language, origin, belief, political or other convictions, as well as financial or social status or other circumstances is not acceptable, the Reform Party and SDE state, pointing to the associated constitutional requirement to any Estonian government.

The outline for a potential coalition also stresses the importance of the professional and independent working of the state's institutions, including an independent judiciary and the apolitical arrangement of the work of authorities like the prosecutor's office, the police, the security authorities and educational and cultural institutions.

The agreement also stresses the importance and the inviolability of the freedom of speech, of the media and other personal freedoms.

Perhaps as a hint at the announcement of chairman of the Conservative People's Party of Estonia (EKRE), Mart Helme, that much like Trump in America and Salvini in Italy his party's ministers will use their new positions as a bully pulpit rather than to consider a more moderate rhetoric, the principles as outlined by Reform and SDE also stress the importance of transparency, courtesy and decency in the way the state communicates with its citizens.

Concerning social issues, the two parties stress that they want to move towards a "gender-balanced society" focused on more equal opportunities in the professional, family and social spheres. The pension system "is sustainable and needs to be developed further."

Although representing only a very small deviation from earlier plans and policies, Reform and SDE's principles take on the meaning of a radical alternative at least in social terms when compared to the already signed coalition agreement between the Centre Party, EKRE and Isamaa.

For the coalition of Reform and SDE to come into being, Ms Kallas will need the backing of at least 51 members of the Riigikogu. The Reform Party and SDE together have just 44 mandates, which means they need another seven votes that would have to come out of the parliamentary groups of Centre, EKRE or Isamaa.

The ready-to-go coalition of the latter three parties has a combined 56 votes in the Riigikogu.