The diplomatic effort, which the Kremlin announced earlier Saturday, follows weeks of escalating tension over Russian encroachment on its neighbor. A senior administration official said Friday that U.S. intelligence had concluded the Kremlin was planning an offensive against Ukraine as soon as next year involving an estimated 175,000 personnel.

 The diplomatic effort, which the Kremlin announced earlier Saturday, follows weeks of escalating tension over Russian encroachment on its neighbor. A senior administration official said Friday that U.S. intelligence had concluded the Kremlin was planning an offensive against Ukraine as soon as next year involving an estimated 175,000 personnel.