Sweden and its Nordic neighbour Finland ended decades of military non-alignment and applied to join the US-led defence bloc in response to Russia's invasion of Ukraine.

Turkey and fellow NATO member Hungary -- both pushing a more accommodating line with Russia -- were the last of the 30-member alliance to ratify Finland's membership this year.

Unanimous backing is needed for new countries to secure the guarantees afforded by the world's most powerful defence alliance, but both Ankara and Budapest have yet to ratify Sweden's entry.

The Western defence alliance will meet in Lithuania's capital Vilnius for a two-day summit set to start from July 11.

Hungary's vote on Sweden's accession is listed in a document titled "Plan of the National Assembly's June-July 2023 session" published earlier this week on the assembly's website, although no exact date is mentioned.

The Hungarian parliament's spring session will end Friday with the accession vote not included on the agenda.

However, an "extraordinary summer session" follows which was "expected to end on July 7", the parliament's press office told AFP in an email.

Hungary's ruling right-wing party Fidesz led by Prime Minister Viktor Orban has complained that Stockholm has unfairly criticised Hungarian government policy.

On Wednesday, US Republican senator James Risch reportedly halted a $735-million (679 million-euro) sale of arms including HIMARS missile launchers to Hungary over its delay on ratifying Sweden's membership.

Hungary's defence ministry dismissed the move, saying Budapest has "no intention of purchasing a HIMARS missile system".

Turkish President Recep Tayyip Erdogan also rebuffed growing international pressure on Ankara to ratify Sweden's NATO bid ahead of the summit.