Republican U.S. Sen. Ron Johnson, of Wisconsin, says he still intends to vote against the GOP tax bill unless changes are made.

Johnson told reporters on a conference call Monday that "we are working very diligently with other Senate Republican colleagues who have similar concerns to fix the problems."

Johnson says the proposal doesn't cut business taxes enough for "pass through" partnerships and corporations. Those are businesses in which profits are passed onto the owners, who report the income on their individual tax returns.

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Johnson is set to vote Tuesday in the Senate Budget Committee on the measure.

"If we develop a fix prior to committee, I'll probably support it but if we don't I'll vote against it," Johnson said.

Johnson said President Donald Trump has assured lawmakers there will be changes.