HELSINKI, Finland — Finnish President Alexander Stubb has outlined his vision for a much larger European Union, saying the 27-nation bloc needs to "think big" and seize the moment to project power on the global stage.

Speaking at an energy conference in the Finnish capital on Wednesday, Stubb said the EU should push to increase its membership to 40 states and named the U.K., Canada, Turkey, Norway and Iceland as potential candidates to join.

His comments come as the Trump administration's actions, alongside Russia's war with Ukraine, prompt some countries to reconsider the benefits of EU membership.

Stubb told the Eurelectric Power Summit that "the window of opportunity" for EU enlargement "is quite short because when the war in Ukraine ends and perhaps when the U.S. administration changes, I don't know, then people are going to take their foot off the gas pedal and start heckling about unnecessary stuff again."

Stubb added that "European strategic autonomy or European geopolitical power" is "often based on size and scale and I think the best European policy ever has been European enlargement."

"In this moment, we need to think big and geographically, we need to enlarge or at least create memberships which are flexible enough to bring in a sum total of 40 European states — or even non-European," Stubb said.

The European Commission, the EU's executive arm, did not immediately respond to a request for comment from CNBC.

The EU is pursuing its largest enlargement in a generation, with nine candidate countries all eyeing entry to the bloc over the coming years. Montenegro and Albania are seen as the frontrunners among the Western Balkans, while Ukraine and Moldova are moving closer to opening formal membership talks.

Finland's president said the EU should look to its western flank and bring the U.K., which left the bloc in 2020, back into the fold, or at least "as close as possible."

Canada should be considered as another option, Stubb said. "Wouldn't it be lovely if Canada was the 28th state of the European Union rather than the 51st state of the United States?"

U.S. President Donald Trump has touted his ambitions of annexing Canada. In a Truth Social post earlier in the week, Trump wrote "51st state!" while sharing a Bloomberg news article about Canada entering a technical recession for the first time since 2020.

Canadian Foreign Minister Anita Anand has previously said that the country is looking to diversify its trade relationships and "really double down on this middle power initiative," referring to an idea laid out by Prime Minister Mark Carney at the World Economic Forum earlier this year.

Stubb told the conference that after looking at Ukraine, Moldova and Georgia, "we need to think seriously about Turkey."

"No one is talking about Turkey anymore, and we need to open our minds to understand that at least from a security perspective, Turkey needs to be as close as possible," Stubb said.

"Then you go to the south or southeast, we look at the Western Balkans, I mean that is the hottest spot in Europe … it's super important. What do we do with Serbia, Kosovo, Albania, Montenegro, North Macedonia? What are we doing with Bosnia and Herzegovina?" he added.

"And then finally, the ones that are really close to my heart, if you go up north, is Iceland, which is holding a referendum, and then Norway," Stubb said.

"We need to start thinking big if we want to project power in the world. But who is going to do this, when, where and how, I don't know," Stubb said.

Iceland's parliament recently voted in favor of holding a referendum on Aug. 29 on whether to begin EU accession talks. The small Nordic country had applied to join the EU in 2009 in the wake of the global financial crisis, before suspending membership talks four years later.

Former Icelandic Prime Minister Katrín Jakobsdóttir previously told CNBC that she didn't see the argument for joining the EU, adding the country already maintains close economic collaboration with the bloc and its citizens enjoy high living standards.

"If a majority of the people wants to apply, it is very important to listen to that majority, but I haven't changed my position," Jakobsdóttir told CNBC in mid-April.

Norway is reportedly reconsidering its relationship with Brussels as it navigates a power struggle between the U.S. and China. Oslo has twice rejected EU membership.