What caused nikita khrushchev to refuse to attend the peace summit in paris in 1960?

The downing of a U-2 spy plane by the Soviet Union

Answergranulation;

The us is first  the  u.s. economy  remains the  largest in the world  in terms of nominal  gdp. however, the  u.s. economy  loses its spot as the number one  economy  to china when  measured  in terms of  gdp  based on ppp. in these terms, china's  gdp  is $23.19 trillion exceeds the  u.s. gdp  of $19.42 trillion