BEIJING, Nov 7 (Reuters) - China"s trade surplus with the United States was $40.75 billion in October, Reuters calculations based on customs data showed on Sunday, down from $42 billion in September. For the first ten months of the year, the surplus was $320.67 billion. Earlier in October, U.S. Trade Representative Katherine Tai pledged to exclude some Chinese imports from tariffs while pressing Beijing over its failure to keep some promises made in a "Phase 1" trade deal made under the Trump administration.