A senior Chinese diplomat has defended a sea gas pact between China and Japan as "transitional," saying it did not compromise national sovereignty.

Chinese Vice Foreign Minister Wu Dawei told reporters on Thursday that this week's agreement to jointly develop gas fields in the East China Sea will not affect Chinese claims to sovereignty over the area's waters.

"For the sake of driving China-Japan relations forward smoothly, the two countries have reached an interim agreement to prevent the issue of sovereignty over the East China Sea from impeding the steady development of bilateral relations."

Wu Dawei described the agreement as the harbinger of a "historic starting point" for ties with Tokyo, and said it did not harm China's claims to much of the sea.

He said China's stance of not recognizing the "median line" of demarcation in the sea has not changed. He stressed that the Chunxiao gas field is within China's sovereign sphere, and that it has nothing to do with common exploration.

China and Japan have held several rounds of talks since 2004 to resolve the dispute over the sea boundary in the East China Sea. The two countries reached a consensus to push for an early settlement of the issue during Chinese President Hu Jintao's state visit to Japan last month.