"I see no other way than to go with the strong transatlantic relations and strengthening NATO, showing that we are united," Budrys said.

"We see that not all countries in Europe take this responsibility seriously," he added, referring to southern Europe, but without mentioning any specific country.

Positioned on NATO's Eastern flank, Lithuania has been a close ally of Ukraine since the beginning of the full-scale Russian invasion in 2022.

The former Soviet-occupied Baltic state has invested 5.4 percent of its GDP in defence -- higher than NATO's five percent target for member states to reach by 2035.

"That's the largest in the whole of NATO and the whole free world, what we are spending," Budrys said.

Earlier this week, NATO's top commander, US Air Force General Alexus Grynkewich, called Lithuania a "wonderful example to follow" in terms of its defence contributions.

Lithuania has committed to cross-European defence -- being the second country in the EU after Poland to sign a European loan programme allocating over 6.3 billion euros ($7.35 billion) in funds to its military and permanently stationing a brigade of 4,800 German soldiers on its territory.

But Budrys -- a former senior inspector in Lithuania's State Security Department -- emphasised that such actions cannot replace the transatlantic alliance.

European security measures are "an important element, complementary to NATO, but not as a substitute to NATO", he said.

"All these other ideas that are coming about the autonomous Europe doing whatever on our own, I'm surprised that they are most often coming from the capitals that are doing least concerning defence," he added.

- Ukraine 90 billion loan 'not enough' -

"Everyone has to (pay their) share, and now it doesn't happen," Budrys said, naming the Nordics, Baltics, Poland and Germany as examples of countries he says do allocate sufficient funding to defence.

"When we go south, less and less finances are dedicated to Ukraine," he added, emphasising that "EU financing through a support loan of 90 billion ... is not enough".

A political independent invested heavily in security, Budrys, who is also a former presidential advisor, has made NATO and maintaining relations with the United States his top priorities since beginning his tenure in 2024.

"The lesson from the Cold War is that we can deter. So the Soviets were deterred, and Russia can be deterred, and not with talks," he said.

"So spend and show how you're building your capabilities," he added.

Bordering Russia's Kaliningrad exclave and Moscow's close ally, Belarus, Lithuania -- like many other states on NATO's Eastern flank -- has experienced drone incursions into its territory, as well as an influx of smugglers' balloons from Belarus.

While mitigating the threat, Budrys underlined that Lithuania and its allies "should take these incidents as an opportunity ... not only as another reason to blame ourselves".

Ahead of the next NATO Summit -- set for Ankara in July -- he stressed that "this is an opportunity to fill the gaps, and maybe also to show the other nations that there are solutions.

"We already did in so many other fields, be it the economic resilience, be it the cultural resilience, and any other sphere," he added.