"We have an obvious and common view when it comes to Ukraine and Russia: This war should end as soon as possible, and not on the aggressor's terms, but on fair and just terms so that peace is lasting," Tusk said at a joint news conference in Warsaw.
The war in Ukraine dominated Tusk's one-on-one talks with Radev, he said, as Russia launched air attacks on targets in Ukraine near Poland's border.
Tusk said two border crossings with Ukraine had been evacuated because of the strikes.
He said Poland would continue working closely with Ukraine and warned other European countries to prepare for a difficult period in the coming weeks and months.
"Autumn and winter could really be critical," Tusk said.
Tusk also said Poland and Bulgaria had "great potential" for cooperation in defence, industry, science and innovation.
"The European heart is beating more strongly today in our region," Tusk said. "I am convinced that Europe’s future belongs to countries such as Poland and Bulgaria."
Radev said Poland and Bulgaria had long-standing historical and cultural ties and shared similar views on European issues.
He praised Poland’s economic growth over the past decade, particularly in advanced technology and defence.
"Poland is no longer a European country that is catching up; Poland is a strong European player with high defence capabilities," Radev said.
The two countries also need affordable energy and support the import of US liquefied natural gas, Radev said.
He said Poland could develop supplies from the north and Bulgaria from the south, while the two countries could also cooperate on nuclear energy.
Radev said Bulgaria was interested in working with Poland in defence, the space sector and advanced technology.
He added that the two countries shared similar views on the security of NATO's eastern flank.
The two prime ministers were also asked about a US invitation to Russian President Vladimir Putin to attend the G20 summit in Miami on December 14-15.
US Secretary of State Marco Rubio announced the invitation on Wednesday, saying it could give Putin an opportunity to meet with President Donald Trump and other world leaders.
Radev said communication channels should remain open during a conflict of such intensity and that every opportunity for talks about peace should be used.
"We have no interest in this war of attrition continuing," Radev said.
Tusk said he would support Putin’s participation if it could bring the sides closer to a just peace.
But he said he feared that "at the current stage" Moscow could interpret the invitation as encouragement to continue its aggression against Ukraine.
Tusk said Poland and Bulgaria should deepen their bilateral ties and thanked Radev for preparing a draft agreement aimed at strengthening cooperation.
He said the two governments would continue working on its details and suggested that a visit to Sofia could provide an opportunity to finalise the process.
Radev said he hoped the talks would continue in Bulgaria.
(gs)
Source: IAR/PAP