Is this endgame position a theoretical win or draw? The following tactics problem comes from ChessTempo, and was taken from a game between Anatoly Karpov and Alexey Kuzmin. It's white's move.

The idea of the problem is to find white's best move from the shown position.

But my question is slightly different: If both players play perfectly from the position shown in the diagram, can white force a win, or can black force a draw?

[FEN "8/3Q2pk/5p1p/5P2/5K1P/p3r3/b2n2P1/8 w - - 0 1"]


I tried using a few chess engines to analyze the position, leaving them running for hours. White gets a very favorable evaluation (about +4 or +5 depending on the engine). I'd normally consider this to be enough for a certain win. But after looking at the computer's best line it seems that after initially winning some material, white's queen just goes round in circles without making any further progress while the black king sits safely behind the wall of pawns. 

I guess either the position is a draw, or the computer isn't able to plan far enough ahead to find the winning line. I can't see an easy way for white to win, but I'm no expert and it's possible I've overlooked something.

So what do you think: is it a theoretical win for white or can black escape with a draw?
I think that the position is a theoretical draw.

While Freeman's answer is quite good, but I think he has overlooked that 1. Qxd2 leads to a clearly drawn position because of Black's amazing response 1 ...Rb3!!

[FEN "8/3Q2pk/5p1p/5P2/5K1P/p3r3/b2n2P1/8 w - - 0 1"]

1. Qxd2 Rb3!! 2. Qxa2 Rb2!! 3. Qxa3 Rxg2


Now I don't see any way for White to win. Black has created an impenetrable fortress and white's queen can do nothing.

The 2400+ rated player Alexey Kuzmin missed the move 1... Rb3 in the game, playing instead 1... Re5? which gives a theoretically losing position. All the engines I tried also miss the sequence 1... Rb3 and 2... Rb2 and instead play a losing move.

I suggest that if there is a forced win for White then we must start looking at 1.Kxe3. This move doesn't win as much material as 1. Qxd2, but it leads to a more dynamic position. White can prevent Black from promoting thanks to black's wrong-colored bishop that is unable to protect the a1 square. White can also threaten to advance the g-pawn to attempt to disrupt Black's wall of pawns.

However a computer analysis of 1. Kxd3 seems to show that despite White's material advantage Black can still get a draw.

I'm no expert, so there may be a mistake in my analysis, so please correct me if I'm wrong.