Ambassador in Moscow Averell Harriman letter to Roosevelt (my translation)
I plan on the next occasion without witnesses to tell Molotov that for sure you don’t wish to mention your name as the one who discussed border issues.
US Department of State, FRUS, tome III 1944, page 1323
Whole story is precisely described in following book:
A Question of Honor by American authors Lynne Olson and Stanley Cloud
You might find interesting also following book:
I Saw Poland Betrayed: an American Ambassador Reports to the American People by former US ambassador in Poland Arthur Bliss Lane
Also I did not write that US had obligation to defend Poland. The US had not any right to recognize illegal government and ignore legal one. Most of Central European countries sided with axis, so one could say cynically that they deserved. Polish case what completely different.
“Border issues were decided already in Teheran 1943”
As I said, waging war on the Soviets to drive them out of Eastern Europe was never an obligation, so no betrayal could have occured.
“The US had not any right to recognize illegal government and ignore legal one.”
I’m not sure what you mean by an ‘illegal government’. If you mean a non-elected government, then the idea that the U.S. has no right to recognize a non-elected government is incorrect. As a sovereign nation, the U.S. can recognize any government it wishes. What authority are you referring to when you say the U.S. has no right to recognize non-democratic governments? And how would the U.S. be able to win the cold war against the Soveit Union without recognizing, and working with, the non-democratic adversaries of the Soviet Union? Taking away this right would be a direct violation of U.S. soverienty and act as an impediment to U.S. interests abroad.