This paper examines the relationship between the current account and budget balances by means of a threshold cointegration approach advocated by Hansen and Seo (2002). Using US data covering 1947–2009, a long-run positive cointegrating relationship is confirmed. This supports the notion of a Keynesian twin deficits relationship. The short-run dynamics are investigated through an estimated threshold vector error correction model. Depending on the regime present, it is either the external or internal balance that is responsible for error correction. This has important implications for the use of fiscal policy to control the external balance.