The dispute over the region, a mountainous territory inside Azerbaijan controlled since the 1990s by ethnic Armenians, flared in 2020 into a six-week war in which Azeri troops regained swathes of territory. The two sides agreed to work on a peace plan after Russia brokered a ceasefire.
Pashinyan, quoted by Russian and Armenian news media, said Azerbaijan was politicising peace efforts, including the issue of building a rail link through Armenia between Azerbaijan and its western enclave of Nakhichivan.
The target of large protests in recent weeks accusing him of making too many concessions on Karabakh, Pashinyan also said more than 50 Armenian servicemen faced treason charges.
While Pashinyan and Azerbaijan President Ilham Aliyev have held a series of meetings in the past 18 months, progress towards a peace treaty has been slow.
"Azerbaijan refuses to talk, publicly accusing Armenia of refusing to talk," Armenia's Armenpress news agency quoted Pashinyan as telling an online news conference. "My assessment is one: it is done to legitimise a new war against Armenia."
On the allegations against Armenian officers, Russia's TASS news agency said Pashinyan told reporters that "a great many affairs are now happening behind closed doors and the public is unaware of them ... More than 50 serviceman are accused of espionage and treason."
The TASS account gave no further details.
Aliyev last week accused Armenia of inaction on the treaty.
Armenia was failing to abide by its "legal obligations" to allow free access for construction of the rail line, Azerbaijani media quoted him as saying after talks with Russian Foreign Minister Sergei Lavrov.
Pashinyan said Aliyev was blocking progress on the issue by linking it to the return to Armenia of prisoners of war.
(Reporting in Winnipeg by Ronald Popeski; editing by Richard Pullin)
