The U.S. formally joined the main organization combating maritime piracy in south Asia on Tuesday, throwing its weight behind a multi-national effort to secure some of the world's busiest shipping lanes.

A map inside the IMB's (International Maritime Bureau) Piracy Reporting Centre (located in Kuala Lumpur) shows where pirate attacks have been occurring in recent years.

As CNBC reported last week, piracy is mushrooming in the area of the Strait of Malacca and Singapore Strait, a shipping bottleneck that sees one-third of the world's annual commercial maritime traffic, making it the busiest waterway on earth.

The U.S. becomes the 20th member of ReCAAP, a Singapore-based organization that's working against maritime crime in the region. Piracy there increasingly includes not just quick robberies but the theft of entire cargoes—especially fuel oil and other petroleum products, which pirates sometimes siphon off onto their own tankers.

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"U.S. membership in ReCAAP will enable us to support multilateral cooperation in addressing the common threat of piracy and robbery against ships in the region's critical sea lanes and waters," a U.S. State Department official told CNBC on Tuesday.

The Strait of Malacca and Singapore Strait handle all of the Persian Gulf oil that makes its way to the big economies of Asia, including China, Japan and South Korea. It also handles most trade between Europe and China.

"The high-risk waters of the Strait of Malacca are a concern for our U.S.-flagged vessels," Robert Gauvin, executive director of piracy policy at the U.S. Coast Guard, said last week. He added that joining ReCAAP will "provide a higher level of security and lessening of the threat to those vessels."