MADRID, July 30 (Reuters) - Spanish utility Iberdrola  faces claims worth up to $535 million in an arbitration process launched by Singaporean liquefied natural gas (LNG) company Pavilion Energy over a supply contract, according to Iberdrola's earnings report.

The dispute is related to a 2019 contract, under which Pavilion supplies natural gas to Iberdrola.

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Pavilion is seeking between $233.4 million and $534.9 million, plus interest, in compensation from Iberdrola in "an amount equivalent to the estimated loss" due to what it called "exceptional circumstances" that had arisen since the contract was signed, according to the document.

Iberdrola said, however, that the contract does not contain a price review clause and it believes "that the agreement between the parties as set out in the contract must prevail".

A spokesperson for Iberdrola declined to comment while Pavilion did not immediately reply to a request for comment outside usual business hours in Singapore.

The case is ongoing in Madrid and subject to Spanish law, Iberdrola said.

The specific amount claimed will be specified during the proceedings, it added.

In June, Shell agreed to buy Pavilion Energy from global investment company Temasek.

(Reporting by Pietro Lombardi, Editing by Louise Heavens)