Separation of Powers in US Constitution

Read the fact pattern provided and post responses, as directed.

Fact Pattern

After the dictator of an African country was deposed, the president of the United States extended official recognition to the country's new government. As ambassador to the newly recognized government, the president nominated a member of his family who had no apparent qualifications for the position. The president's political opponents in the Senate passed a resolution requiring all consular staff below the rank of ambassador to be selected from a list of candidates approved by a majority of the Senate. The president refuses to obey the resolution.

Prompt

Please post an analysis of the issues raised by this dispute. There is a separation of powers between COngress and the President (executive branch). Who has the main role in appointing ambassadors to a foreign government according to the Constitution? The congress have a say in approving the President's appointment so how do they resolve this dilema if the Senate has a different requirement and it passed a law to direct the President on how to select an ambassador?