Yellen: Negative interest rates not part of an active discussion

The Federal Reserve kept interest rates unchanged on Wednesday, meeting most market watchers' expectations. The central bank also expects to raise rates twice this year.

Oil prices extended gains following the announcement, while the dollar fell broadly against major world currencies.

In a news conference, Fed Chair Janet Yellen said the central bank is concerned it has not seen a significant uptick in inflation. "Hopefully inflation is moving up," she said.

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