June is out. July might be too soon. The Federal Reserve’s next interest-rate increase is coming, but even September isn’t a sure bet.

That’s the message investors and economists are taking from Chair Janet Yellen’s remarks Monday. Her comments were the last the public will hear from a Fed official before the central bank’s policy-setting meeting next week.

In her remarks, Yellen was clear that she’s fairly sure the economy will improve enough to warrant another interest-rate increase. She also has lingering uncertainties that may take several months to resolve.

The Fed chair underscored her sense that the U.S. economy still has forward thrust and that consumers were in a position to provide a “significant” step up in spending this quarter to propel overall growth. But she was silent on when another rate increase would be needed, playing down a June move and raising doubts about July.

“I see good reasons to expect that the positive forces supporting employment growth and higher inflation will continue to outweigh the negative ones,” she said in Philadelphia before the U.S. central bank enters a self-imposed quiet period before its June 14-15 policy meeting.

“I continue to think that the federal funds rate will probably need to rise gradually over time to ensure price stability and maximum sustainable employment in the longer run,” she said.

The questions she raised about the disappointing May jobs report, the weak pattern of investment spending, international risks, and sagging inflation expectations could take months -- not weeks -- to resolve, making a rate hike when the policy committee meets next week less likely, economists said.

“The Fed needs to see a rebound in the second quarter followed by that extending into in the third quarter,” said Neil Dutta, head of U.S. economics at Renaissance Macro Research LLC in New York, who predicts the Federal Open Market Committee will hold rates steady next week and in July. “I think the data will be there.”

If the committee keeps rates on hold next week, it will be the fourth consecutive meeting at which it has delayed a move, underscoring the unusual, gradual pattern of monetary policy in an economy that still bears deep scars from the recession.

“When would it be appropriate to resume normalization of interest rates? What she really said today was: ‘I have no idea.” And it was the right answer,” said former Fed Governor Laurence Meyer, who now heads the Washington firm LH Meyer Inc. “Normalization is a concept. There is no time frame.”