**Headline:**
**"Trump Adopts Unyielding Trade Posture, Excludes Tariff Negotiations with Mexico and Canada"**
**Rationale:**
- **"Adopts Unyielding Trade Posture"** conveys a firm, strategic stance, enhancing the original "declares" with a stronger tone.
- **"Excludes Tariff Negotiations"** clearly indicates the refusal to engage in discussions, maintaining clarity while using active language.
- Specifying **"Mexico and Canada"** retains focus on the key nations involved without adding external context (e.g., NAFTA), staying true to the original headline.
This version balances journalistic rigor with conciseness, emphasizing Trumpโs inflexible position while preserving the core message.