  We investigate the optical emission-line flux ratios of narrow-line regions,
in order to determine whether the formation of AGN jets requires specific
accretion conditions. We find that bright compact radio galaxies, which are
powerful radio galaxies in the early stage of the jet activity, exhibit
systematically larger flux ratios of [O{\sc i}]$\lambda$6300/[O{\sc
iii}]$\lambda$5007 and smaller flux ratios of [O{\sc iii}]$\lambda$5007/[O{\sc
iii}]$\lambda$4363 than radio-quiet (RQ) Seyfert 2 galaxies. Comparing the
observed line ratios with photoionization models, it is found that the
difference in the flux ratio of low- to high-ionization lines (e.g., [O{\sc
i}]$\lambda$6300/[O{\sc iii}]$\lambda$5007) can be well understood by the
difference in the spectral energy distribution (SED) of ionizing sources.
Powerful young radio-loud (YRL) AGNs favor SED without a strong big blue bump,
i.e., a radiatively inefficient accretion flow (RIAF), while RQ AGNs are
consistent with the models adopting SED with a strong big blue bump, i.e., a
geometrically thin, optically thick disk. These findings imply that the
formation of powerful AGN jets requires the accretion disk with harder ionizing
SED (i.e., a RIAF). We discuss the obscuring structure of YRL AGNs as a
plausible origin of the difference in flux ratios of [O{\sc iii}]$
\lambda$5007/[O{\sc iii}]$\lambda$4363.
