Sea trials of the Admiral Gorshkov aircraft carrier being overhauled for the Indian navy at the Sevmash shipyard in northern Russia have been postponed until the beginning of June, the shipyard said on Wednesday.

The purchase of the Soviet-built Admiral Gorshkov was agreed in 2005 but delivery to India has been long delayed. The cost of refurbishing the aircraft carrier, to be renamed INS Vikramaditya, has since gone up from $947 million to $2.3 billion.

“The start of the sea trials has been moved to the beginning of June,” a Sevmash spokesman said.

The vessel was originally scheduled to sail for trials in the White Sea and the Barents Sea on May 25.

The delay could have been caused by poor weather forecast in the trials area next week, the official said.

The delivery of the Admiral Gorshkov to the Indian navy is expected in December 2012.