It has both an irregular and regular form. You can use both and both are correct.
Strived or Strove? The past participle is more complicated. Striven is the traditional form, but strived has gained ground and is now more common. So, for example, I have striven five years is the traditional construction, but I have strived five years is acceptable to modern English speakers. Constructions like I have strove five years are still rare, though.
Example: Trump has striven to improve relations between Washington and Moscow during his time in office