MANILA, Philippines — The world’s largest ships are robustly regulated and safe to sail even as their dimensions expand, according to the United Nations agency that sets global maritime rules.

Regulators haven’t let vessels, especially cruise ships, get so large that they present a hazard, according to Koji Sekimizu, Secretary-General of the London-based International Maritime Organization. The growing size of vessels is under scrutiny after the Costa Concordia cruise ship grounded last month, killing at least 17 people. China tightened rules last week that have restricted the world’s biggest iron-ore carriers from calling at its ports, citing “hidden dangers.”

“I think our standards are very robust,” Sekimizu said in a Feb. 2 interview in London, insisting such developments don’t reflect any shortcomings in the IMO’s rules covering ship design and safety. “We haven’t established any limitation based on scale when it comes to safety requirements, however, we can make sure all the ships are safe.”

The IMO’s remit includes ensuring the safety of and preventing pollution from a global fleet that it says exceeds 100,000 vessels and carries 90 percent of global trade. It’s up to the commercial market to decide the most appropriate size for vessels and the IMO won’t impose restrictions, Sekimizu said.

The Costa Concordia, measuring 290 meters (951 feet) in length, was carrying 4,200 passengers and crew on a Mediterranean cruise when it struck rocks on Jan. 13 near Giglio, Italy. The ship, owned by Carnival Corp., the largest cruise line owner, has berths for 3,780 passengers, the fourth- biggest by that measure, according to data from Clarkson Research Services, a division of the world’s largest shipbroker. The Oasis of the Seas and the Allure of the Seas, each with 5,400 berths and owned by Royal Caribbean Cruises Ltd., are the largest, the data show. The Norwegian Epic, with 4,200 berths, is third.

Sekimizu, director of the IMO’s safety division from 2004 until his appointment as secretary-general in December, said the agency spent a decade developing rules for the largest cruise ships that were implemented in 2010. He urged against pre- judging the cause of the Costa Concordia grounding, and said he expected to learn the outcome of the Italian authorities’ inquiries into the incident in “several months.”