Hello.

Please tell me if it's possible to say:
1) to declare a message;
2) to announce a message;
3) to sound a message;
4) to voice a message;
5) to present a message;
(for example, Diplomats ... a message from the United Nations.)
Thank you very much for your help.

To say or write this, will not make sense:

Diplomats to declare a message from the United Nations.

That is not a complete sentence. What are you REALLY trying to say?

to announce a message

Hello! I'm here to help you understand the different ways to express the act of conveying a message. Let's go through each option you mentioned:

1) To declare a message: This phrase is commonly used when an official or authoritative statement is made, often in a formal or public setting. For example, a government representative may declare a message at a press conference.

2) To announce a message: This phrase implies making a public statement or proclamation to inform others about important news or information. For instance, a speaker may announce a message at a public event to share something significant.

3) To sound a message: This phrase suggests that a message is communicated audibly or by producing a sound. For example, a siren might sound a message to alert people of an emergency.

4) To voice a message: This phrase indicates speaking or expressing a message verbally. It implies using one's voice to convey the intended information. For instance, a spokesperson may voice a message during a media interview.

5) To present a message: This phrase means showcasing or delivering a message in a formal or organized manner. For example, a speaker may present a message at a conference or seminar using various visual aids, such as slides or videos.

As for your example regarding diplomats and the United Nations, you could say "Diplomats delivered a message from the United Nations," as it implies that the message was conveyed by diplomats on behalf of the organization.

Remember, context and intention play important roles in determining which phrase is most suitable for a particular situation.