In making the announcement, Bulgarian Interior Minister Tsvetan Tsvetanov said the attack could have been financed by Hezbollah, the Sofia News Agency reported.
The July attack killed five Israeli tourists, the bus driver and a suicide bomber.
The interior minister said the two identified individuals have been living in Lebanon, the home of Hezbollah, since 2006.
Bulgaria had delayed implicating Hezbollah in the attack to avoid damaging relations with other European nations while facing pressure from the United States, The New York Times reported.
Germany and France regard Hezbollah as a legitimate political organization and treat it as a benign group, allowing it to raise funds in their countries.
The United States and other Western countries consider Hezbollah to be a terrorist organization.
Tsvetanov told reporters Tuesday Bulgarian authorities had traced the suspects' activities in Australia and Canada "so we have information about financing and their membership in Hezbollah."
"Bulgaria's implication of Hezbollah underscores the importance of international cooperation in disrupting terrorist threats," the White House said in a statement. "We call on our European partners as well as other members of the international community to take proactive action to uncover Hezbollah's infrastructure and disrupt the group's financing schemes and operational networks in order to prevent future attacks."