OSAN, South Korea (Reuters) – The United States flew four F-22 stealth fighter jets over South Korea on Wednesday in a show of force following North Korea’s recent rocket launch and ahead of the allies’ joint military drills next month aimed at deterring Pyongyang’s threat.

The flight of the radar-evading F-22s, based in Okinawa, Japan, is the latest deployment of key U.S. strategic military assets to the South after the North defied warnings from world powers and conducted a fourth nuclear test last month.

South Korea and the United States said the North’s rocket launch on Feb. 7 was a long-range missile test and violated U.N. Security Council resolutions that ban the use of ballistic missile technology by the isolated state.

North Korea said it was a satellite launch.

The U.S. military said at the weekend that it had deployed an additional Patriot high-velocity missile interceptor unit to South Korea in response to recent North Korean provocations.

The allies were also expected to begin discussions on the deployment of the advanced Terminal High Altitude Area Defense (THAAD) missile defense system.

Last month, the United States flew a B-52 bomber capable of carrying nuclear weapons on a low-level flight over the South following the North’s Jan. 6 nuclear test.

The joint military drills scheduled to start in March, which in most years last eight weeks and involve hundreds of thousands of South Korean and U.S. troops, will be the largest ever, according to South Korean officials.

There are 28,500 U.S. troops stationed in the South as part of combined defense with the South’s military of more than 600,000. The North has an army of 1.2 million.

North Korea claims the annual drills are war preparations. South Korea and the United States say the exercises, which have been conducted for years without major incident, are defensive.

(Writing by Jack Kim; Editing by Michael Perry)