(Reuters) - Armenia's government on Thursday gave approval to a bill that calls for the country, once part of the Soviet Union, to launch a bid to join the European Union.

Armenia has in recent years deepened ties with the West at the expense of its traditionally close relations with Moscow, which it has accused of failing to defend it from longtime rival Azerbaijan.

The bill was drawn up following a successful petition.

In a document seen by Reuters, the government backed its introduction to parliament, saying it would represent "the beginning of the accession process of the Republic of Armenia to the European Union".

Brussels did not immediately respond to a request for comment.

Three other former members of the Soviet Union - Estonia, Latvia and Lithuania - have joined the bloc, a years-long negotiating process requiring harmonisation with EU legislation, among other things.

Armenian Prime Minister Nikol Pashinyan underlined to the cabinet on Thursday that the public should not expect a rapid accession, and that it would in any case require approval by referendum.

In 2023, Pashinyan told the European Parliament that Armenia was ready to move as close to the EU as possible, although he stopped short of backing full membership.

Kremlin spokesman Dmitry Peskov told reporters that Russia needed to understand Brussels' position, and that Armenia could not join the EU while remaining a member of the Eurasian Economic Union, a trading bloc of some post-Soviet countries.

Though Armenia's relations with the EU are warm, joining will not be easy.

The landlocked, mountainous country of 2.7 million people shares no border with the EU and has been in conflict with Azerbaijan, a major gas supplier to EU countries, since the late 1980s.

Azerbaijan in 2023 mounted a lightning offensive to retake control of Nagorno-Karabakh, a breakaway region that had been run for more than three decades by its ethnic Armenian majority with Yerevan's backing, prompting its population to flee.

This week, Azerbaijani President Ilham Aliyev said Armenia presented a "fascist" threat that had to be destroyed, in what Yerevan said might be a prelude to fresh conflict.

(Reporting by Felix Light; Additional reporting by Dmitry Antonov and Bart Meijer; Editing by Kevin Liffey)