The Federal Reserve's reduction of asset purchases could mean a short-lived rally in bonds, JPMorgan Private Bank Director of Fixed Income Heather Loomis said Tuesday.

Loomis said that she expected the Fed to reduce its purchases of U.S. Treasury bills by $10 billion per month and mortgage securities by $5 billion per month.

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"And if they come in right at that line, we actually think that there could be a bit of a relief rally to the tune of about 5 to 10 basis points on that," she said on CNBC's "Fast Money."

The Fed's asset purchases stand at $85 billion per month.

"We've never had an opportunity to witness this before in markets with a non-economic buyer at play," Loomis added, speculating that at this point the market had "probably internalized that the data set is getting better in the U.S.

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"Direction of rates has to be up from here," she added.

Loomis also said that the bond market would likely be looking at the proportion of any Fed's tapering, which is widely expected.

"I think they want to see a mixture and just not one or the other," she said.

— By CNBC's Bruno J. Navarro. Follow him on Twitter @Bruno_J_Navarro.

— CNBC's Katie Young contributed research to this report. Follow her on Twitter: @katiecnbc.

Trader disclosure: On Sept. 17, 2013, the following stocks and commodities mentioned or intended to be mentioned on CNBC's "Fast Money" were owned by the "Fast Money" traders: Joe Terranova is long VRTS; Joe Terranova is long MS; Joe Terranova is long GS; Joe Terranova is long OXY; Joe Terranova is long HOS; Joe Terranova is long HAL; Joe Terranova is long APC; Joe Terranova is long LTD; Joe Terranova is long SBUX; Joe Terranova is short XBI; Josh Brown is long AAPL; Simon Baker is long AAPL ; Simon Baker is long BAC; Simon Baker is long C; Simon Baker is long GS; Simon Baker is long JPM; Simon Baker is long WFC; Simon Baker is long SBX; Simon Baker is long FB; Simon Baker is long AMZN; Simon Baker is long EEM; Simon Baker is long GM; Simon Baker is long P; As of 9/12 Jon Najarian is long AAPL; Jon Najarian is long FB; Jon Najarian is long MSFT; Jon Najarian is long LULU; Jon Najarian is long GRPN; Jon Najarian is long P; Jon Najarian is long ORLY; Jon Najarian is long SYK; Jon Najarian is long MGM; Jon Najarian is long WYNN; Jon Najarian is long MAR; Jon Najarian is long CERN; Jon Najarian is long COP; Jon Najarian is long FIO; Jon Najarian is long GPS.