It said it did not intend to militarise the area and accused the US of provocations by sending a navy ship through the area last month.
The comments by a Chinese vice foreign minister came on the sidelines of the annual Asean summit in Kuala Lumpur.
China claims most of the South China Sea as its territory, but four South-East Asian states also claim parts.
On Wednesday, US President Barack Obama called on China to stop land reclamation in the disputed waters.
China has repeatedly said its dredging work is legal.
The land reclamation, which began in late 2013, has turned submerged reefs into islands.
https://www.endtime.com/wp-content/uploads/2017/06/86819907_a2ab0eb8-84f2-47ce-b322-8a4d2e851309.jpg 371 660 alphatimes https://endtime.com/wp-content/uploads/2020/06/endtime-logo.png alphatimes2015-11-23 00:00:002018-03-28 17:03:11China defends building projects on disputed islands