The speech, which the campaign has said will highlight a "half century of Joe Biden failing America", will seek to shore up the Republican's support in the state.
Given questions over the U.S. move, diplomats said Russia, China and other countries are likely to simply ignore it and not reimpose the sanctions on Iran.
Harris will likely aim to speak directly to millions of women, young Americans and voters of color, constituencies the party needs if Biden is to defeat Republican Trump.