MANILA, Sept 5 (Reuters) - The Philippine central bank will shift from passively holding gold to actively trading the precious metal with the aim of keeping it at around 10% of total international reserves, its governor said on Saturday.

The Philippine's reserves totalled $98.6 billion as of the end of July, with gold accounting for 13%, thanks to an increase in international bullion prices, and giving the central bank an opportunity to sell some of its gold.

Bangko Sentral ng Pilipinas Governor Benjamin Diokno said the monetary authority plans to maintain an "optimal" ratio of gold to total international reserves, which studies say should be at 10%.

"The Monetary Board decided to shift from passive to active trading largely because of the change in the price dynamics of gold," Diokno told reporters in a phone message. He said the central bank was not trading gold earlier.

Gold broke above $2,000 per ounce in August, making the precious metal one of 2020's best performing mainstream assets.

Diokno was elaborating on remarks he made on Friday, when he revealed the central bank was considering selling gold to bring down the ratio to 10%, and keep it there.

The bank "will always be opportunistic in its reserves management," Diokno said.

(Reporting by Karen Lema; Editing by Tom Hogue & Simon Cameron-Moore)