What is the just Islamic course of action regarding two wives, in the event that the first wife refuses the husband marrying a second wife and demands divorce, while the husband wishes to keep both of them?

Allah has permitted a man to marry up to four women, on condition that he deals justly with them. If he fears he cannot be just, then he should content himself with one. It is not permissible for a woman to seek a divorce because her husband has married another. The husband is advised to keep both wives and be just between them, and warned against inclining towards one over the other, for the Prophet, peace and blessings be upon him, said: "Whoever has two wives and inclines to one of them over the other, will come on the Day of Judgment with his side leaning."