In the event the State or a county thereof enters upon privately owned real property by authority of an agreement to acquire the real property either by voluntary action of the parties or by condemnation, the State or county is required to:
If the State or county does not so complete its part of the agreement, the State or county shall pay to the property owner, in addition to the sum due, interest of six per cent a year on the sum due commencing with the end of the term of two years, and the property owner may bring suit against the State or any county to recover the sum together with interest.
HRS § 101-3