"Public prosecution received information from the Turkish side through the Joint Working Group between the Kingdom of Saudi Arabia and Turkey that indicates that the suspects in that incident had done their act with a prior intention", the statement said.
Turkey has other "information and evidence" about the killing by Saudi officials after Khashoggi entered the consulate on October 2, and it will eventually reveal that information, Erdogan said without elaborating.
The Saudi change of tack came after Central Intelligence Agency director Gina Haspel reportedly heard an alleged audio recording of the killing during a fact-finding visit to Turkey this week.
Mr Trump also said it was "possible" Crown Prince Mohammed bin Salman did not know about the killing.
After a succession of denials that Riyadh had anything to do with his disappearance, the kingdom eventually admitted that Khashoggi had died, but said it was in a fight with Saudi officials who had embarked on an unsanctioned extradition operation.
USA and foreign officials say such an operation - involving a team of Saudi agents - was unlikely to have taken place without the knowledge of the kingdom's leaders, including ambitious Crown Prince Mohammed bin Salman.
Saudi Arabia's public prosecutor said Khashoggi's killing was premeditated, contradicting a previous official statement that it happened accidentally during a tussle in the Saudi consulate in Istanbul.More news: 'I Am Bringing Out Military for This National Emergency' at Border
As global pressure has grown, President Trump has promised "severe punishment" if the Saudi government - a close ally of the USA - was found to be linked to the killing.
The minister also said the administration of US President Donald Trump has a "rational, realistic" foreign policy that all Gulf Arab states can support. "I think people have assigned blame to Saudi Arabia with such certainty before the investigation is complete".
"We will overcome" the consequences of the Khashoggi killing, he added. All four of Khashoggi's children are now in the U.S.
Trump has condemned Saudi Arabia's shifting account of the killing of Khashoggi as "the worst cover-up ever".
But he said that Secretary of State Mike Pompeo had revoked the visas of Saudis suspected in the killing and that Trump had vowed "to get to the bottom of it" and get Congress involved. Turkish media have published details of his alleged torture and decapitation.
Erdogan and Trudeau stressed the need to shed light on the killing and the importance of punishing the culprits, said a source from Turkish presidency, who asked not to be named due to restrictions on speaking to the media.
Though Mattis made blunt remarks about the incident involving United States resident, he said the killing would not diminish ties with Oil-rich Saudi Arabia.