As China develops more powerful electronic devices, it has become determined to keep the details secret (so their electronic wonders will not be easily defeated in wartime.) To that end, they have requested that the United States eliminate the use of aircraft and ships to monitor activity along the Chinese coast. Most of this is electronic surveillance. Some is simply keeping an eye on what the Chinese are building (in the way of military facilities along their coast.) The U.S. recon operations take place in international air and sea space, but the Chinese know that this does not stop the Americans from picking up lots of useful information. China has implied that if the U.S. does not cease this snooping, there will be more confrontations with Chinese aircraft and ships. Similar confrontations took place with Russia during the early years of the Cold War. Dozens of American military personnel were killed. China is also trying, without success so far, to unilaterally modify international law, to extend its territorial waters (that other nations cannot enter).
But the effort is important. For example, last year the U.S. revealed what the American Navy EP-3 electronic reconnaissance aircraft was spying on, when it was clipped by a Chinese fighter in early 2001. The target was the new naval base China is building in the south. Three years ago, commercial satellite photos began to show details of a new naval base under construction at Yulin, near Sanya, on the southern island of Hainan (near Vietnam). The base has underground docking facilities for nuclear and diesel-electric subs and surface ships, created by tunneling into coastal hills.
Rumors of such a base have been circulating for the previous six years, apparently since locals began noticing all the construction activity, and the tight security around the site. The underground facilities not only protect the boats from air or sea based attack, but enable maintenance and modifications to be done in secret. Apparently back in 2001, the U.S. Navy believed there was enough electronic emissions coming from the construction site to justify sending an EP-3.
The U.S. intelligence community had picked up signs of work on the new base even before the locals began to chatter about something going on there. Several smaller naval bases and navy air fields already exist on Hainan Island, but the new base is shaping up as a major facility, one capable of supporting a much larger fleet than China now possesses. India is particularly concerned because the Hainan base is close to the Indian ocean, and areas where the Indian Navy has long been top dog. Many other nations note the proximity of the new base to the Straits of Malacca, the busiest shipping channel on the planet.
The Chinese also know that the U.S. Air Force and Navy are designing replacements for their current electronic warfare (EW) aircraft. The Navy wants to replace the EW version of its P-3 reconnaissance aircraft (EP-3), while the air force has several elderly aircraft using a wide array of sensors and radars. The navy has decided that sensors have become small enough, and cheap enough, that they can load up a Boeing 737 with radar, sensors, computers, mini-UAVs and the people needed to run it all, and perform functions formerly taken care of by several different aircraft. This new Super Snooper will be the EP-8. It will mount an AESA radar for scanning the sea (or land) below in great detail. Also mounted on (actually, built intp) the aircraft skin are dozens of antennas, for detecting any kind of nearby electronic emissions. The EP-8 would be used for a wider array of missions than its predecessor, the EP-3. In addition to the traditional trolling off the coast of, say, China, North Korea or Iran, to detect how the locals use their electronic devices (radars, communications, whatever), the EP-8 can also fly over combat zones seeking out cell phone, walkie-talkie or other radio use, and locating the people involved. The EP-8 carries missiles, as well as small UAVs that can be used to test enemy air defenses (which can result in a missile to take out the hostile radar).
China knows that all this new tech is coming, and wants to keep it as far away from their coasts as possible. The question is, will China risk war by playing rough to keep the Americans away.