* President seeks 28 pct corporate rate, down from 35 pct * Proposal is Obama's first tax overhaul package * Analysts see remote chance of election-year action * Romney proposes 25 pct corporate rate By Kim Dixon and Rachelle Younglai WASHINGTON, Feb 22 (Reuters) - President Barack Obama made an opening offer in what could be a long negotiation with corporate America on Wednesday, putting forward his first detailed plan to cut the corporate tax rate. Though it has lit