JACKSON HOLE, Wyo., Aug. 27 — As the Federal Reserve fiercely debates how to reduce inflation within the United States, economists are warning that trends outside the country may soon make the Fed’s job much harder.

In recent years, global integration has made things easier for the Fed in two ways. An explosion in low-cost exports from China and other countries helped keep prices of many products low even as Americans spent heavily and loaded up on debt.

At the same time, China and other relatively poor nations reversed the normal patterns of global investment by becoming net lenders to the United States and Europe. Analysts estimate that this “uphill’’ flow of money from poor nations to rich ones may have reduced long-term interest rates in the United States by 1.5 percentage points in recent years — a big difference when home mortgage rates are about 6 percent.

But as Fed officials held their annual retreat this weekend here in the Grand Tetons, a growing number of economists warned that those benign international trends could abate or even reverse.