Prince Saud al-Faisal's comments came on deadline day to reach a framework agreement aimed at stopping Tehran from acquiring nuclear weapons, in exchange for easing crippling sanctions.
Iran insists its nuclear efforts are for purely peaceful purposes.
"If the P5+1 wanted to give Iran a role in the region they should have first looked to favour an entente between Iran and the Arab states," Saud told the Shura Council, an appointed consultative body.
Saud asked the six major nations to not "short-circuit the interests of the states of the region by dangling before Iran benefits that it will not be able to reap without cooperation with the countries of the region."
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Sunni-majority Saudi Arabia has long vied for regional influence with Shiite-dominated Iran.
The kingdom's concern over the outcome of nuclear talks with Iran comes as Saudi Arabia leads an Arab coalition which last Thursday began bombing Shiite Huthi militia in neighbouring Yemen.
Iran warned Tuesday that the Saudi "attack" on Yemen endangers the whole region.