SEATTLE (AP) — One of two groups that submitted plans for a possible renovation of KeyArena is withdrawing from the process, citing issues with how the city has conducted the process.

Seattle Partners — a group that combined arena giant AEG and Hudson Pacific Properties — announced Sunday it is pulling out of the process after submitting plans in April for a proposed $521 million renovation of KeyArena.

Seattle Partners was one of two groups to submit proposals for renovation of the arena. Oak View Group was the other group to submit a proposal — a $564 million plan — and has appeared to be the favorite in the process.

In a letter to Seattle Mayor Ed Murray, Seattle Partners says it believes it has the best plan, but the city has "failed to conduct a sufficiently thorough, objective and transparent process to properly evaluate the respective strengths and weaknesses of the two proposals."