The interest rate on an American home mortgage later this year could depend a lot on how many euros, yen, pesos and rupees a dollar will fetch.
The dollar's steep ascent against many of the world's currencies since last summer could help delay the first Federal Reserve rate hike since 2006. In turn, that could affect mortgage and other long-term rates.
Historically, the Fed officially hasn't paid much attention to the dollar's swings, honoring a separation of powers that goes back to the central bank's creation: The Fed is responsible for monetary policy, while decisions about the dollar are the U.S. Treasury Department's domain.
But under Chairwoman Janet L. Yellen, the...