1000 marbles in a line winning strategy

Question

There is an infinite grid. Two players play a game. Player A places two black marbles in consecutive blocks in his turn, and player B places one white marble in any of the squares. Player A wins, if he gets 1000 black marbles together in a line. However, player B does not have any winning combination, that is even if 1000 whites occur in a row, player B does not win. Show that player A always has a winning strategy.