The only official task of the vice-president is to

1. advise the president in foreign affairs2. preside over the Senate and to vote in case of a tie3. serve as the president's good will ambassador to other countries4. chair government commissions at the President's request

2. preside over the Senate and to vote in case of a tie.

Explanation:

The Vice President of the United States is indirectly elected by the citizens and he is not only an officer of the executive branch but also of legislative branch. He presides over Senate meeting but may not except to vote until a tie-breaking situation occurs. From his selection to the impeachment, all process are present in the Constitution of the U. S.