"After years of recession, Slovenia now has a strong economic growth, which means it can afford to increase defence expenditure," Kacin said in Brussels on Friday.
"It absolutely needs this increase too, because in the austerity years it fell behind with investment, and the armament and equipment need to be modernised and replaced with newer ones."
He believes that Slovenia needs to start fulfilling the goals it had set itself. "It's necessary to move from words to action, from commitment to securing the funds and implementing the planned investment."
Defence spending was a major topic at a NATO defence ministerial in Brussels on Thursday and Friday and will also be in focus at the July summit after US President Donald Trump made it clear he expected European allies to substantially increase their defence budgets.
The allies have made it their goal to try to near the target of spending 2% of GDP for defence as much as possible by 2024.
An unofficial estimate is that Slovenia will allocate 1% of GDP for defence this year, which according to current plans should be increased to about 1.1% of GDP by 2024.
"Slovenia is certainly not the worst," the ambassador said, adding that NATO understood that not all the countries can have plans at the moment that would meet the expectations to a greater extent.
"Slovenia is among those democracies who don't have a fully empowered government at the moment or a parliament that could take such decisions, so we expect the new government and coalition to address these issues in its coalition agreement and seek consensus in the National Assembly."
Kacin, a former defence minister, believes the low defence spending is mainly Slovenia's problem because the army is underfunded so it grapples to secure enough staff and investment and development funds.
The Slovenian Armed Forces, the government and parliament will need to conduct a serious discussion and adjust plans to the changed security situation and new forms of threat, the ambassador said.
Slovenia is to increase its defence spending by about 60% in nominal terms in 2017-2023, which unofficial sources say is comparable to the efforts of many other countries.
There have been suggestions that Slovenia should meet its commitments to NATO as seriously as those related to the eurozone or the Schengen area.