A Taiwan flag can be seen at Liberty Square in Taipei, Taiwan, on July 28, 2022. (Ann Wang/Reuters)

The U.S. State Department said on Monday it approved a possible foreign military sale to Taiwan of spare parts valued at about $228 million, which Taiwan's military said will help maintain combat readiness in the face of China's grey zone intrusions.

The return, repair, and reshipment of spare parts will be transferred from U.S. Government stock, the State Department said in a statement, adding that Taiwan's military will have no difficulty absorbing this equipment into its armed forces.

The United States is Taiwan's most important supporter and arms supplier, despite its lack of formal ties with the island.

Taiwan's defense ministry expressed its thanks for the arms sale package which it said it expected to "become effective" within a month.

"The Chinese Communist's routineised grey zone intrusions have constricted the training space and response time in our air space and maritime areas," it said in a statement.

"The repair and return of the aircraft parts and accessories agreed to be sold by the United States will help maintain the combat readiness and safety of various types of aircraft equipment of the Air Force."

The Chinese regime, which views democratically governed Taiwan as its own territory, has ramped up military and political pressure over the past five years to assert its claims, which Taipei strongly rejects.

The Chinese regime has been stepping up grey-zone warfare, using tactics that stop short of actual combat to test and pressure Taiwanese forces, including regular coast guard patrols near the Taiwan-controlled Kinmen islands that sit within view of China.