House Speaker László Kövér said a strong European Union can only be built on strong nation states.
"No nation state's vital interests can be trampled on in the name of any perceived or real majority," Kövér said after meeting Slovak counterpart Richard Rasi in Budapest on Tuesday.
Referring to a planned ban on Russian energy in the EU, Kövér said: "Hungary and Slovakia are in the most vulnerable position in that respect."
As challenges for the two countries are similar in view of their location and similar economic structure, they need to cooperate in addressing them, he said.
Rasi said that resolving issues around gas supplies showed "helpfulness and cooperation" in bilateral ties, while he also thanked Hungary for contributing to the protection of Slovakia's airspace.
Slovakia and Hungary have similar positions in terms of illegal migration as well as the enlargement of the EU, the Slovak speaker added.