ORLANDO, Fla. (AP) _ Vice President George Bush has defended his referral of a Guatemalan doctor seeking medical help for the Contra rebels in Nicaragua to former national security aide Oliver North.

''Colonel North handled Central America'' for the White House, Bush said, and his reply to a March 1985 letter from Dr. Mario Castejon was routine.

In Guatemala, Castejon said Monday he contacted and met North after Bush suggested in a letter that he do so.

Bush, at a news conference Monday, said he did that despite Congress' ban on military assistance to the rebels seeking to overthrow the leftist Sandinista government because ''it was our (administration's) policy to help the Contras.''

Bush's letter, displayed by Castejon at a news conference in Guatemala City, was dated March 3, 1985.

Reporting on the letter Sunday, the Miami Herald described it as ''the first documentary evidence linking Vice President Bush to North and the secret network he (North) forged to aid the Contras.''

Castejon's letter, which dealt with medical supplies, had nothing to do with North's later involvement in a clandestine plan to ship arms to Iran in hopes of obtaining freedom for Americans held captive by terrorists in the Middle East, said the vice president, a likely presidential candidate who was on a political fund-raising tour of Florida.

North was fired from the National Security Council on Nov. 25 after the disclosure that U.S. arms were shipped to Iran and profits from the sales allegedly went to the Contras.

Craig Fuller, chief of the Bush staff, said after the Miami Herald article on the letter appeared Saturday evening that it had little significance.

''There's no indication that the vice president was aware of anything more than the fact that within the NSC Oliver North was responsible for monitoring activities in Central America related to the Contras,'' Fuller said.

According to the Tower commission report on the Iran-Contra affair, North was deeply involved in a covert operation to support the Contras even though Congress, on Oct. 3, 1984, prohibited government agencies involved in intelligence activities from aiding them directly or indirectly.

The ban was eased later in 1985, when Congress approved $27 million in non- military aid for the Contras. Last year, Congress approved $100 million in military and humanitarian aid.

Castejon said he is trying to organize a political party in Guatemala. In 1985, he said, he helped Contra rebels in both the northern and southern parts of Nicaragua.

''My ties with the Nicaraguan democratic resistance began in 1985 through the Emergency Medical System, a unit in which I assisted with the humanitarian medical aid for the members of the resistance groups in Nicaragua,'' the doctor said.

The private medical group was based in Baltimore, Castejon said.