MADRID, Spain (AP) _ Florida real estate developer Joseph Zappala presented his credentials Monday to King Juan Carlos as U.S. ambassador to Spain.

After the ceremony at the Royal Palace, the new U.S. envoy and the king met privately for 15 minutes.

Zappala's nomination by President Bush set off a round of controversy, but he was confirmed two weeks ago.

According to an editorial in the New York Times in July, the nomination of the 56-year-old businessman was due to ''a distinctively large contribution to the Republican Party, reportedly $126,000.''

Zappala replaces Reginald Bartholomew, who assumed the post in September 1986.

Zappala said last week in Madrid his primary mission would be to strengthen the already excellent relations between the United States and Spain.

The signing in December 1988 of a new eight-year Spanish-American defense agreement that stipulates the withdrawal of approximately one-third of the U.S. forces stationed in the country spelled an end to a period of tension.

Zappala presented his credentials two days before Prime Minister Felipe Gonzalez is to arrive in Washington on his second official visit to the United States since his Socialist Party scored a landslide victory in 1982 elections. Polls indicate Gonzalez will win an unprecedented third term in general elections Oct. 29.