What determines which state is represented by its ambassador in bilateral diplomatic relations?

Question

When sovereign states A and B are conducting some bilateral negotiation, they have a few options:

• A's ambassador can negotiate with B's government
• B's ambassador can negotiate with A's government
• Ambassadors or other representatives of both states can negotiate with each other in another forum, such as the UN or a third state

For example, in The Hunt for Red October, the Soviet ambassador to the United States negotiates with an American official in Washington intermittently over the course of the plot. What factors result in this pairing, instead of the American ambassador to the Soviet Union negotiating with Soviet officials in Moscow?

I have a better understanding of what factors would force the third option (for instance, a lack of bilateral relations between the states involved), but feel free to discuss them, too, especially if they help illuminate the other choices.

Answer 1

One factor is which side is more desiring of plausible deniability. In the Hunt for Red October, the Soviets were in a very delicate situation. The Soviet government meeting with the US ambassador would have meant admitting that there was something that they needed to meet with the US about, and anyone involved in the negotiation would be admitting to being involved. The Soviet ambassador meeting with the US government is easier to spin as just keeping communication channels open, and the top levels of the Soviet government could disavow involvement.

In addition, if the Soviet government had met with the US ambassador, then anything they discussed would then have to be transmitted to from the embassy in the USSR to the US. By having the Soviet ambassador meet with the US government, the Soviet government can give him an initial briefing, and then allow him to deal with further developments as they come up. There was more need for the US to react to the USSR than the reverse, so most of the interaction was in the US.

Another factor is standing. Generally, the country with more standing will send ambassadors to the country with less standing. This doesn't apply to the Red October situation, as the US and the USSR were both superpowers.