The Secretary of State shall perform such duties as shall from time to time be enjoined on or intrusted to him by the President relative to correspondences, commissions, or instructions to or with public ministers or consuls from the United States, or to negotiations with public ministers from foreign states or princes, or to memorials or other applications from foreign public ministers or other foreigners, or to such other matters respecting foreign affairs as the President of the United States shall assign to the Department, and he shall conduct the business of the Department in such manner as the President shall direct.