April 2 (Reuters) - Australia's Austal said on Tuesday it had considered an A$1.02 billion ($661.88 million) takeover offer from South Korea's Hanwha Ocean and it was not "satisfied" that the deal would be approved by Australian and U.S. regulators.

The defense contractor and shipbuilder said Hanwha's offer was for A$2.825 per share, representing a premium of 28.4% to Austal's last closing price.

In November, Austal signed an initial agreement with the Commonwealth of Australia which would see the company being selected as the Commonwealth's strategic shipbuilder at Henderson, Western Australia.

Austal is also a prime contractor designing, constructing and sustaining ships for the US Navy.

It said that Hanwha's offer is subject to regulatory approvals including Australia's Foreign Investment Review Board (FIRB) and U.S. Defense Counterintelligence and Security Agency.

"The company is open to further engagement if Hanwha is able to provide certainty on whether a transaction would be approved," Austal said in a statement. ($1 = 1.5411 Australian dollars) (Reporting by Shivangi Lahiri in Bengaluru; Editing by Alan Barona and Maju Samuel)