For Iran, the most important goal is to secure a sanction relief and the agreement shall lead Iran to boost its weak economy without US interference. Iran asked for $10 billion sanction relief as a good gesture from US which declined. However that emphasized how Iran needed this agreement although it does not necessarily construe Iran will accept all conditions especially under a new hard line administration.
YOUTUBE
US wants a new JCPOA that would not met by the Congress aggression. US Congress is concerned how Iran progressed once the JCOA has been declined by Trump administration. US wants to track the advancement and be assured that Iran will not impose any threat to US interests (USE, Saudi Arabia and Israel) in the region. Moreover, it will relieve US to concentrate on rising China in Asia.
The talks are not to end quickly. Therefore, the Iranian aggressive policy in Iraq, Lebanon and its threat to Saudi Arabia and Israel will not end although a possible agreement might ease the policy for some years since Iran needs investment to boost its economy. However Iran national security will remain intact even if there will be a new JCPOA. Therefore any agreement will be at most beneficial to Iran and US (as boosting economy and concentrating on China) although it will bring prosperity to Middle East for short time or a decade at most since Israel will likely to consider any possible agreement unless Iran waives any nuclear advancement in future.
World is changing continuously. Countries take position to its own needs as time flows. US needs to concentrate on China while Iran needs to boost its economy. However, Israel will not endorse such agreement in long term as long Tehran persuades nuclear advancement programme in coming decades. Therefore, any deal will bring prosperity to region for a short term but tension will still remain intact in long term.
