"The Secretary-General is deeply concerned about the decision by the Jerusalem municipality to advance planning for house demolitions and further settlement activity in the area of Silwan," Ban's press office said in a statement.
"The planned moves are contrary to international law, and to the wishes of Palestinian residents."
Israeli municipal authorities moved ahead on Monday with plans to demolish 20 Palestinian homes in East Jerusalem, risking more U.S.-Israeli friction over a building project seen by Palestinians as settlement expansion.
Ban's statement appeared to confirm that the Jerusalem city planning board's decision would lead to renewed diplomatic pressure on Prime Minister Benjamin Netanyahu.
Earlier this week, Netanyahu bowed to world calls to ease a Gaza blockade after Israel's deadly raid on an aid flotilla.