Factbox-After Bulgaria, euro expansion faces hurdles in remaining EU states

Jan 1 (Reuters) - Bulgaria became the 21st member of the euro zone on Thursday despite opposition from half its electorate, leaving only a handful of countries in the 27-member European Union yet to adopt the currency.

Although public support for the euro is high in some of the remaining countries including Hungary, eurosceptic parties in governing coalitions and parliaments are likely to hold back further expansion of the currency zone for the foreseeable future.

Here are the remaining countries.

HUNGARY

About 72% of the Hungarian public support adoption of the euro, according to an October to November survey by Eurobarometer conducted for the European Commission. This is the highest level of support among the remaining EU countries despite Prime Minister Viktor Orban's euroscepticism.

Opposition leader Peter Magyar has said he would put the country on a course to adopt the euro if his centre-right party wins next year's election.

However, Hungary has the EU's highest debt as a share of economic output outside the euro zone, while its deficit cuts since the COVID-19 pandemic have stalled amid heavy pre-election spending by Orban.

Even if it meets all entry criteria, joining the euro zone will not be possible without a parliamentary supermajority as Orban, who is opposing deeper integration with the EU, has enshrined the forint as Hungary's national currency in the constitution.

ROMANIA

The Central European country is struggling to lower the EU's largest budget deficit, meaning it may take several years to stabilise its finances for it to have a realistic prospect of joining the euro zone.

Public support for the euro is at 59%, the Eurobarometer survey showed.

However, faced with high inflation, austerity measures and a buoyant far-right waiting in the wings ahead of a 2028 election, the subject has faded from public discussion.

POLAND

In Poland, where public support for the euro is at 45%, Finance Minister Andrzej Domanski has said Warsaw is not working on adopting the unit and the EU's largest economy outside the euro zone was "happy to have our own currency".

Jaroslaw Kaczynski, leader of the biggest opposition party, Law and Justice, has said anyone striving to have the euro introduced was "a mortal enemy of Poland".

CZECH REPUBLIC

Czech public support for the euro is at 30%, according to the Eurobarometer survey, and the government has no plans to take steps to adopt it.

Czech national debt levels are still much lower than in most euro zone countries, so for many, entry raises the risk of taking over responsibility for more indebted countries.

Prime Minister Andrej Babis was pro-euro as a businessman and early politician but has since moved his party to national conservative and eurosceptic positions.

He is now proposing enshrining the crown in the constitution.

SWEDEN

Only one small party is openly championing euro zone entry while the populist Sweden Democrats - the second biggest group in parliament whose support is crucial for the right-wing minority government - oppose it, meaning any debate about joining is likely to remain academic.

Sweden joined the EU in 1995 but a referendum in 2003 rejected adopting the euro by a majority of 56% to 42%.

Public support for the euro is at 39% based on the Eurobarometer survey, with opposition to adoption declining from more than 80% in the wake of the 2012-2013 euro zone debt crisis.

DENMARK

Denmark, which joined the EU in 1973, is the only member of the bloc with an opt-out of the euro, meaning it has the right to remain outside the currency area even when all entry criteria are met. Public support for euro adoption is at 33%.

(Reporting by Simon Johnson, Jan Lopatka, Luiza Ilie, Johan Ahlander, Karol Badohal and Niklas Pollard;Compiled by Gergely Szakacs;Editing by Emelia Sithole-Matarise)