Story highlights On Saturday, he re-upped a challenge that he's made to Clinton in the past for her to be clearer about her plans

"Stop being vague on this issue," Sanders said

New York (CNN) Bernie Sanders was combative Saturday morning during a rally stop in Washington Heights in New York City, calling on Hillary Clinton to "stop being vague" about her plan to tax income and increase Social Security benefits.

"Secretary Clinton really has avoided this issue. She has talked about it in generalities. So I would challenge her right today: Are you prepared to lift the cap on taxable income?" he said at the United Palace theater.

Sanders typically talks about Social Security benefits, lamenting that $11,000 to $12,000 a year is not a livable income for seniors and calling it "nowhere near enough" money to survive on. On Saturday, he re-upped a challenge that he's made to Clinton in the past for her to be clearer about her plans for helping these seniors.

"And are you prepared to expand benefits for millions of seniors and disabled veterans who need it? Stop being vague on this issue. Yes or no, are you going to lift the cap?" he continued.

Sanders has called for a lift of the cap on taxable income, which currently stands at $118,500. The Clinton campaign did not immediately return a request for comment.

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