The underlined word in the passage is "solicitation." In this context:
Meaning:
"Solicitation" means a request, appeal, or entreaty made by one party to another. In this passage, it refers to Japan's request or entreaty to the United States.
Tone:
The tone associated with "solicitation" in this passage is diplomatic and formal. It suggests that Japan formally requested or approached the United States for something, likely related to peace negotiations in the Pacific. It implies a sense of official communication between nations.