Why didn't western democratic leaders try to stop the building of the berlin wall

They didn’t try because tensions betweenness the US and the USSR where at the work thanks to the U2 (An American spy plane) incident. Thanks to this the USSR didn’t even want to talk about nuclear test agreements with the US. And since the last time the blockade happen was it almost started WW3. Since diplomacy doesn’t work ,force would just cause WW3. Besides the allies can just drop supply’s in East Germany ,since if the USSR shot them down it would give an excuse for America to have a war.