Greene was a convert to Roman Catholicsm and a British patriot. One of his latter books "Monsignor Quixote" (my very favorite book of all time)is a heart warming celebration of Christian faith vs Communist propoganda. I can't recommend it highly enough.
I have read several Greene novels and have never perceived any sympathy for communism.
http://www.firstthings.com/ftissues/ft9911/opinion/royal.html
In a 1987 speech Greene gave in Moscow, he claimed to have observed a new thing: "We are fightingRoman Catholics are fightingtogether with Communists, and working together with Communists. We are fighting together against the Death Squads in El Salvador. We are fighting together against the Contras in Nicaragua. We are fighting together against General Pinochet in Chile." Gorbachev, who was present at this speech, was only two years away from pulling the plug on the Latin Communists, their Catholic sympathizers, and his own USSR. Greene concluded: "I even have a dream, Mr. General Secretary, that perhaps one day before I die, I shall know that there is an Ambassador of the Soviet Union giving good advice at the Vatican."