The country’s foreign minister said information about a probe into Rakhmat Akilov was passed to Sweden via another Western nation.
Abdulaziz Kamilov also told reporters that Akilov had been recruited by IS after he left Uzbekistan to live in Sweden in 2014.
The minister did not say which country the information was first passed to and Swedish authorities have not yet commented on the claims.
An Uzbek security source, speaking anonymously, said this week that Akilov had been detained at the Turkish-Syrian border in 2015 and was deported back to Sweden.
Akilov’s lawyer has said his client has admitted committing a terrorist crime.
He told a court the 39-year-old had confessed to deliberately driving the stolen beer lorry into crowds along Drottninggatan in the Swedish capital on 7 April.
Four people, including a British man, were killed and 15 others injured.
The Uzbek construction worker had an asylum request rejected by Sweden last year and was arrested several hours after the attack in a Stockholm suburb.
He was already wanted by police for failing to comply with a deportation order.
Security services previously said Akilov had expressed sympathies with extremist organisations, including IS, but had not been viewed as a threat.