Most U.S. Federal Reserve officials see a growing risk of trade disputes potentially damaging their positive economic outlook, according to minutes of the central bank's most recent monetary policy meeting.

The Federal Open Market Committee, which raised its benchmark interest rate at the June 13 meeting, has signaled it may hike rates twice more this year if its current outlook holds up. But the minutes of that meeting showed that FOMC participants see increased risks to those forecasts.

"Most participants noted that uncertainty and risks associated with trade policy had intensified and were concerned that such uncertainty and risks eventually could have negative effects on business sentiment and investment spending," the minutes said.

The release of the minutes came as the United States and China were due to begin imposing an additional set of tariffs on each other, on top of steel and aluminum tariffs the U.S. has put in place.

Fed officials are continuing to hear concerns from their business contacts about the ongoing trade discussions, the minutes show. Some of those contacts said their "plans for capital spending had been scaled back or postponed as a result of uncertainty over trade policy."

Fed Chairman Jerome Powell said June 20 that the Fed has not seen any negative effects from trade policy show up in economic data. But he also noted that the trade discussions "could cause us to have to question" the central bank's current outlook.

Overall, though, FOMC voting members continued to believe gradual rate hikes remain appropriate amid a "strong economy that was evolving about as they had expected."

Fed officials suggested they may begin tightening monetary policy in the coming years after years of keeping interest rates at extra low levels. The minutes show they generally thought they should hike their benchmark rate by 2019 or 2020 to a level "at or somewhat above" what they view as the longer-run federal funds rate.

A number of them also believe "it might soon be appropriate" to adjust their post-meeting statement to show that their monetary policy stance would no longer be stimulative.

They also expect the unemployment rate to continue dropping below its current 3.8% level, helping drive up inflation figures. The Fed's preferred inflation gauge had been hovering just under the central bank's 2% target at the time of the meeting, though more recent data showed it reached that goal in May. Fed officials thought it was "premature to conclude" that they met their target on a sustainable basis, with a few saying inflation expectations remain below the 2% mark.

Other Fed officials took a more cautious tone on whether inflation could start seeing unhealthy increases. "Some participants raised the concern that a prolonged period in which the economy operated beyond potential could give rise to heightened inflationary pressures or to financial imbalances that could lead eventually to a significant economic downturn," the minutes say.

They also continued to disagree on whether a flattening yield curve was showing signs of concern. Some Fed officials said the yield curve's reliability of predicting future recessions may have lessened, though a number of officials "thought it would be important to continue to monitor the slope of the yield curve."