"The purpose of consolidating these two networks is to mainstream environmental issues, improve synergies, better integrate core operations, and ensure that we strengthen our focus on sustainability as we increase our investment in infrastructure," Wolfowitz said in an email to World Bank staff, seen by Reuters.

To address concerns that environmental issues could be dwarfed by the bank's increased spending on infrastructure projects, Wolfowitz said he would create a new position for a world-class environmental expert to strengthen the role of the bank's environment team.

"It is crucial that we maintain the bank's leadership role in emphasizing the importance of sustainability in development," Wolfowitz said.

In addition, Wolfowitz outlined the responsibilities of his two new top deputies, in a move he said would produce stronger results for the development agency.

He said Graeme Wheeler, the bank's former treasurer and ex New Zealand treasury official, will oversee Europe and Central Asia, South Asia, Latin America and the Caribbean.

Juan Jose Daboub, former finance minister of El Salvador who officially starts as managing director on Wednesday, will manage Africa, the Middle East and North Africa, East Asia and the Pacific.

Previously, the bank's operations were overseen by Shengman Zhang, who left what was then the lone managing director post in January.

Wolfowitz said the division of labor provided each managing director with a good balance of poor countries and emerging economies.

The move is the latest in a row of cautious changes to the bank's senior management by Wolfowitz, who came under fire at the start of his term a year ago for surrounding himself with American advisors.