Beijing has set a population cap of 2 million for the high-profile Tongzhou district, its municipal subsidiary administrative center, to ensure the center's healthy growth, the capital's deputy mayor said on Thursday.

"Beijing will take steps to avoid a population boom in Tongzhou district," Li Shixiang said.

The eastern suburb has a registered permanent population of 870,000, Li said.

The capital also set itself a maximum population of 23 million, not far above the current population of more than 21 million.

Building of a new subsidiary administrative center in Tongzhou will draw approximately 400,000 residents from downtown to the suburban district, the Beijing Municipal Commission of Urban Planning said.

In addition to the administrative shift, the move is also expected to promote tourism and commerce in Tongzhou, the commission said.

The deputy mayor made the remarks at a news conference out-lining achievements in the integrated development of Beijing, Tianjin and Hebei province.

Transferring some of the municipal administration from downtown to the eastern suburb could facilitate Beijing focusing on its core functions as a national capital and ease urban problems like traffic congestion and pollution.