Andrzej Duda made the remark during a speech in Bodzentyn, southern Poland, on Thursday, Polish state news agency PAP reported.
The president visited the southern town to mark 160 years since the start of Poland's 1863 January Uprising against Russia.
The people of Bodzentyn played an active part in the insurrection, according to historians.
‘With modern weapons it is possible to repel Russia’
Duda told the audience that, amid Russia's assault on Ukraine, Poland was buying new weapons, “tanks, gun howitzers, artillery rocket systems and air-defence systems.”
He added: “We are completing all the successive stages of strengthening the Polish army so that no one attacks us, so that it doesn’t pay for anyone to attack us.”
The president told the gathering: “With modern arms, with weapons that are sophisticated, that perform excellently and that are brilliantly suited to the battlefield, it is possible to repel the assault from countries such as Russia.”
He added: “That is why we need modern weapons. Yes, they are expensive, but they are the best in the world.”
‘National security is my biggest concern’
Duda went on to say: “Today, for me, as the president for whom you voted, and whom you elected, the biggest concern is to ensure that you are able to live and work in peace, that you are able to raise your children in peace, in a free, independent and sovereign country.”
He declared: “Today, for me, as president of the Republic of Poland, ensuring such security is an absolutely fundamental and most important concern.”
The president's speech came as Russia’s war against Ukraine continued for the 337th day.
(pm/gs)
Source: PAP, prezydent.pl, kielce.tvp.pl