Tusk was speaking as the prime ministers of the four countries met for their first summit in more than two years.
The meeting was hosted by Hungarian leader Peter Magyar in the town of Gödöllő near Budapest. It marked the first summit of the Visegrad Group at the prime ministerial level since February 2024.
Speaking at a joint news conference after the talks, Tusk thanked Magyar for what he described as "restoring hope" that the Visegrad Group could "once again play a leading role" in European affairs.
"If we understand that what unites us is stronger than what divides us, Europe will start listening to us," Tusk said.
He cited energy policy, migration, agriculture, geography and shared history as areas of common interest among the four Central European countries.
"When we act together, we will be able to present our ideas even to the largest powers," Tusk said. "The V4 itself can become one of the major powers. Everything depends on whether we return to the way we worked years ago, based on trust, mutual loyalty and understanding."
Hungary's Magyar said all four leaders supported deeper regional cooperation and wanted to focus on delivering tangible results.
Among the projects discussed was a proposed high-speed rail link connecting Warsaw, Prague, Bratislava and Budapest. Magyar said he hoped the project could secure funding from the European Union.
"Central Europe is one of the most dynamically developing regions of the European Union," he said.
Slovak Prime Minister Robert Fico said the four countries would work to coordinate their positions more closely and hold regular meetings ahead of European Council summits.
He identified energy prices as a key area for cooperation and outlined priorities for Slovakia's upcoming presidency of the Visegrad Group, which begins on July 1.
Those priorities include improving regional competitiveness, reducing economic disparities, lowering energy costs, supporting EU enlargement and combating illegal migration, Fico said.
Czech Prime Minister Andrej Babiš also highlighted high energy prices as a major concern, Polish state news agency PAP reported.
He said the leaders discussed Russia's war in Ukraine, migration, the future of the Visegrad Group and a NATO summit scheduled for July in the Turkish capital Ankara.
Asked about the deterioration of cooperation within the V4 in recent years, Magyar said relations between Poland and Hungary had suffered because former Hungarian Prime Minister Viktor Orban pursued a policy toward Russia that Poland could not accept.
"The issue was Hungary's relationship with Russia," Magyar said.
The leaders said they were not considering expanding the Visegrad Group's permanent membership but were open to inviting other countries to participate in discussions on specific issues.
Fico said the prime ministers of Germany and Austria could be invited to future talks on energy and migration.
Before the summit, Magyar said strengthening the region's competitiveness would be the main topic of discussion. Other priorities included reducing energy dependence, developing north-south transport links, expanding cooperation in research and innovation, and rebuilding trust within the Visegrad Group.
The Visegrad Group was established in 1991 to promote cooperation among Poland, Hungary, the Czech Republic and Slovakia. The alliance has faced strains in recent years, particularly over differing approaches to Russia following Moscow's 2022 invasion of Ukraine.
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Source: IAR, PAP