Liberal leader Jan Björklund normally works with the centre-right parties in the Alliance coalition, but in an interview with newspaper Dagens Nyheter he says if the 2018 election produces another deadlock then his party is ready for a centre-right and centre-left government.
"In that situation it is the Alliance that can decide how Sweden shall be governed, says Björklund to Swedish Radio. Then we have three options: one is that the Alliance works with the Sweden Democrats. I don't want that. The other is another december Agreement. I think that has been a bad experience, it has given the Left Party too much influence. So then, if we exclude both the parties on the fringes, it only remains for the parties in between work together more."
Jan Björklund says it is important for centre parties to keep out "populists" of right and left.
He says the current government, backed by the Left Party, has given this former Communist party too much influence. He says that a centre-right government backed by the Sweden Democrats would also be bad, because of that party's "anti-democratic roots" and unreliability.
"Both are extremist parties that should be shut out of political power. They are elected to the parliament, but and must be treated correctly, but government politics in Sweden should not build upon either of these parties," says Jan Björklund to news agency TT.
The proposal has been welcomed by the Social Democrats, who would like to break up the Alliance by wooing the more liberal parties away from the traditionally conservative Moderates.
Jan Björklund says to Swedish Radio that working with the Social Democrats is a logical step for his colleagues in the centre-right Alliance.
Moderate Party leader Anna Kinberg Batra says to TT her aim is to bring down Social Democrat Prime Minister Stefan Löfven, "and form a better government."
In the 2014 election the Liberals (then known as Folkpartiet) received 5.42 per cent of the vote. Neither political bloc received a majority, but the Social Democrats formed a government, and became the biggest force in parliament because of Left Party backing.