South Korea recently confirmed that it is not buying American SM-3 anti-missile missiles for its three Aegis equipped destroyers or for use on land based Aegis systems. Instead South Korea is buying PAC-3 anti-missile missiles for its land based Patriot systems and developing its own anti-missile missile with capabilities similar to the SM-3. South Korea has built a substantial arms industry in the last two decades and wants to demonstrate that it can handle really high-tech stuff (like anti-missile systems).
South Korea has already bought Standard 2 (SM-2 Block IV) anti-missile missiles for its three Aegis destroyers. This version is effective against ballistic missile warheads that are about to hit their target. In one test, a SM-2 Block IV missile destroyed a warhead that was only 19 kilometers up. The more specialized (and twice as expensive) SM-3 missile can destroy a warhead that is more than 200 kilometers up. But the SM-3 is optimized for anti-missile work, while the SM-2 Block IV is good to use against both ballistic missiles and aircraft. South Korea has also purchased the anti-aircraft version (Block IIIB) of the SM-2 for their Aegis destroyers.
This turn away from the SM-3 came as a surprise to many. In 2012 South Korea put the third "Sejong The Great" class destroyer into service. This may be the last of these Aegis equipped warships for South Korea. The first one entered service in 2008 and South Korea wanted to build six, but the expense appears too great. These ships are also called KDX-III (Korean Destroyer Experimental) class guided missile destroyers and were designed to operate far from South Korea. Building six was part of a plan to give South Korea an international (or at least regional) naval capability. That plan changed in 2010 after North Korea sank a South Korean corvette with a torpedo and later shelled a South Korean island off the west coast. Since then South Korea has scrambled to build more coast protection vessels and enhance anti-submarine capabilities. It was believed that SM-3 for the three KDX-IIIs was to be part of this.
Meanwhile South Korea already has a very potent navy. The KDX III was preceded by the 3,900 ton KDX-I in 1998, and the 5,500 ton KDX-II in 2002. The 9,900 ton KDX-IIIs are approximately the same size as the U.S. Navy's Arleigh Burke class guided missile destroyers. Actually, the KDX III is a little larger than the Burkes and have 128 VLS cells for missiles, compared to 96 on the Burkes. The VLS tubes usually carry 80 SM-2 anti-aircraft missiles, 32 cruise missiles, and 16 rocket launched anti-submarine torpedoes. There are also six anti-submarine torpedo tubes. There is also a 5 inch (127mm) gun, two 30mm auto-cannon, and a multiple cell launcher of Rolling Airframe Missiles for anti-missile defense. The KDX can also carry two helicopters. The KDX-III is the first Korean ship large enough to carry the AEGIS system and was always expected to get the SM-3 upgrade (which some Japanese Aegis ships have). Built in South Korea the KDX IIIs cost about $930 million each. South Korea likes the Aegis radar because it can spot any missile launch in North Korea and that is seen as sufficient as South Korea has other systems for knocking down North Korean rockets and missiles.