This paper studies the effects of government guarantees on the interconnection between banking and sovereign debt crises in a framework where both the banks and the government are fragile and the credibility and feasibility of the guarantees are determined endogenously. The analysis delivers some new results on the role of guarantees in the bank-sovereign nexus. First, guarantees emerge as a key channel linking banks’ and sovereign stability, even in the absence of banks’ holdings of sovereign bonds. Second, depending on the specific characteristics of the economy and the nature of banking crises, an increase in the size of guarantees can be beneficial for the bank-sovereign nexus in that it enhances financial stability without undermining sovereign solvency.

We develop a model where banks invest in reserves and loans, and trade loans on the interbank market to deal with liquidity shocks. Two types of equilibria emerge, depending on the degree of credit market competition and the level of aggregate liquidity risk. In one equilibrium, all banks keep enough reserves and remain solvent. In the other, some banks default with positive probability. The latter equilibrium exists when competition is weak and large liquidity shocks are unlikely. The model delivers several implications concerning the relationship between competition, aggregate credit, and welfare.

Loan guarantees represent a form of government intervention to support bank lending. However, their use raises concerns as to their effect on bank risk-taking incentives. In a model of financial fragility that incorporates bank capital and a bank incentive problem, we show that loan guarantees reduce depositor runs and improve bank underwriting standards, except for the most poorly capitalized banks. We highlight a novel feedback effect between banks’ underwriting choices and depositors’ run decisions, and show that the effect of loan guarantees on banks’ incentives is different from that of other types of guarantees, such as deposit insurance.

This article highlights a novel channel through which the level of deposits matters for bank fragility and efficiency. We augment a global-game model of bank runs with a consumption-saving choice that determines deposit size in the initial period. We derive two key results. First, depositors’ incentives to run increase with the amount of savings held as bank deposits. Second, a saving externality emerges because individual depositors fail to internalize the impact of their deposit decisions on the likelihood of a bank run. This leads to depositors’ over-saving and inefficient bank liquidity provision, as well as excessive bank fragility. Finally, we characterize the optimal policy to implement the efficient allocation.