China's aircraft carrier, known as the Varyag, has completed its ninth sea trial, the longest yet, and returned to the Port of Dalian in northeastern Liaoning Province yesterday.

China's aircraft carrier platform returns to the dock in Dalian, northeast China's Liaoning Province, after finishing its 9th sea trial, July 30, 2012. The trial lasted 25 days, the longest one in its history.

However, military officials confirmed it will continue to carry out tests rather than be commissioned today as predicted by some experts.

In photos: Aircraft carrier platform finishes 9th sea trial

There are still many tests to be done before it can become a combat platform, Lin Bai, a colonel of the General Armament Department of the Chinese People's Liberation Army, told a press conference yesterday.

"The Great Wall wasn't built in a day, we hope people can treat the issue rationally and objectively," Lin said.

The sea trials have been running smoothly so far and attained anticipated objectives, while the next tests and training tasks had yet to be decided, he added.

Five tugboats drew the vessel back into port yesterday morning after the 25-day sea trial.

The carrier first carried out tests in the north Bohai Sea and then headed further east for a one-day exercise in the Yellow Sea on Sunday, China News Service reported.

The aircraft carrier still has many parts to be tested, including an important step called electromagnetic compatibility, said Song Zhongping, a military commentator. This will ensure that equipment or systems will not interfere with each other or prevent each other's correct operation.

It will be closer to its commissioning when we see if aircraft can take off and land on the deck of the carrier freely, Song said.

He said the carrier would be equipped with a defense system able to launch attacks on missiles, aircraft and approaching vessels.

The carrier will also use a Chinese radar system that can evaluate risks automatically and had a strong anti-interference capability.

The nation's first carrier, refitted from former Ukraine vessel Varyag, left port on August 10 last year for its first sea trials and since then has regularly been tested in both the Yellow and Bohai seas.

Some military experts believed that the carrier would be commissioned today on China's Army Day, but officials denied that.

"I have heard of no such a plan," Yang Yujun, a defense ministry spokesman, said earlier.