Emerging-market leaders would appreciate it if the Federal Reserve opts against further tapering of its bond purchases this week.

But their troubles may actually make the decision to taper easier for the Fed.

Financial markets have been singed by a series of flare-ups around the world over the past week, including worries over weak economic data from China, protests in Ukraine, and sliding currencies in Turkey and Argentina. Layered on top are worries that as the Fed reins in its bond buying, the flow of credit in emerging markets will be stanched.

It isn't clear how much of a role the Fed's bond-buying program has had in supporting emerging-market economies. What matters more, though, is that enough investors believe it has played a part. In their view, if the Fed keeps paring back its purchases even as things already look a little dicey, real trouble could follow.

If market strains intensify enough in the lead up to the Fed's policy decision Wednesday, it may opt to take a timeout—not because of warm feelings for other economies, but because falling U.S. stocks might prompt companies to grow cautious all over again.

Yet the Fed is also left with the paradoxical possibility of Treasury yields falling even if it signals faster tapering to come. As investors have retreated to America's relative safety, the yield on the 10-year note has fallen to a two-month low of 2.74% from 3% earlier this month. So even if the Fed eases up further on quantitative easing, it has less to worry about in terms of causing a jump in mortgage rates as the U.S. housing market heads toward the key spring buying season.

With concerns put on hold that tapering would lead inexorably to higher long-term rates, the Fed will likely feel comfortable tapering some more.