July-August 1939: What were the French and Brits Offering Russia?

I'm reading The Rise and Fall of the Third Reich (one month in, 35% complete, LOL) and I'm up to August 1939, the month before Hitler invades Poland. During this time there were competing negotiations simultaneously going on between Russia and Germany along with France/England and Russia. Russia was basically "shopping" for a treaty. Germany wanted a non-aggression pact guaranteeing that Russia would not intervene when they invaded Poland. Germany knew it could not quickly defeat Poland if Russia came to Poland's aid. It also knew that France and England would immediately press war on the western front of Belgium and Holland and Germany did not want to be fighting France and England in the west and Russia in the east.

France/England wanted Russia to guarantee that they would help defend Poland in case Germany invaded. (FWIW, Poland rejected any Russian help, complicating French/England efforts.) But it's unclear what France and England were offering Russia to intervene in Poland. I've searched for an answer to this but I've come up empty. Germany was promising not to attack Russia in case they invaded Poland. Just what was France/England offering Russia in case Germany invaded Poland? I can't seem to find an answer.