DIPLOMACY : U.S. Officials Crisscrossing S. Africa : Washington is Pretoria’s biggest trading partner. Political disagreements don’t strain economic ties.

When U.S. Energy Secretary Hazel O’Leary arrives today in Cape Town, leading nearly 100 aides, energy experts and business leaders on a weeklong visit, she may have to get in line.

American officials have crossed the country all week. Massachusetts Gov. William Weld toured with a trade delegation from his state. And nine mayors, from Newark, N.J., to Albuquerque, N.M., wandered in search of sister cities.

“I’ve encountered a lot of skepticism from people saying, ‘Oh, it’s just another bunch of Americans,’ ” said an exasperated advance man for O’Leary in one of several calls pleading for coverage of his boss. “But this is pretty high-level, substantive stuff. Really!”

Whatever O’Leary accomplishes, however, she already has been upstaged. Iran’s foreign minister, Ali Akbar Velayati, met with President Nelson Mandela on Thursday at the end of a highly publicized three-day visit during which he signed agreements for a bilateral commission, enhanced trade and, most important, oil. Lots of oil.

Roelof F. (Pik) Botha, minister of mineral and energy affairs, said South Africa plans to sign a deal to allow Tehran to store up to 15 million barrels of crude oil near Cape Town for sale in the region.

The deal, which also lets South Africa buy Iranian oil, flies in the face of Washington’s largely unsuccessful attempts to persuade the world to impose trade sanctions on Tehran because of its support of international terrorism and its drive to develop nuclear weapons. But Botha was hardly apologetic.

“Not a single European country” has honored the embargo, Botha told a news conference. “Why should South Africa? It is clearly not in our interest, and I hope our American friends will now start to understand that we have our own interests at heart.”

Asked about the U.S. objections, Botha replied, “We don’t care. This is not the first time that the U.S. has been against our cooperation with other countries. They have failed in their policy.”

That was a reference to another American complaint. South Africa not only has exchanged ambassadors with Cuba, it has invited Cuban President Fidel Castro for a state visit. Castro attended Mandela’s inauguration and is lauded here for his longtime opposition to apartheid.

South Africa’s deputy foreign minister brushed aside a complaint from the U.S. House of Representatives subcommittee on Africa. “Although the Cold War is over, the United States still conducts a Cold War policy toward Havana,” Aziz Pahad told Parliament.

U.S. Ambassador Princeton Lyman has requested a meeting with South Africa’s foreign minister, Alfred Nzo. But Lyman has denied that relations are strained, insisting that Washington’s close ties to Mandela’s government are not endangered by the Iranian deal or other recent disputes.

Indeed, the United States has become South Africa’s largest trading partner since the end of apartheid-related sanctions in 1993, with an estimated $4 billion in annual bilateral trade. Washington is also the largest aid donor, appropriating $181 million this fiscal year and $528 million over the last three years for investment, housing, training and other development assistance.

Even the aid has been a sore point, however. In an odd display of pique last November, Mandela called the aid package “peanuts” and “very limited support indeed.” Although he apparently confused dollars with less valuable rand, the South African monetary unit, his blunt comments unnerved supporters in Congress fighting efforts to slash foreign aid.

Other issues also rankle. In April, the Clinton Administration placed South Africa on a low-level “watch list” of nations that don’t honor intellectual property rights because of a dispute over alleged trademark infringement.

Then came the chickens. A shipload of frozen chickens from Florida sailed into Cape Town last month to find new, increased import duties.

The incidents, although minor, have led to a bout of U.S. bashing in the press here, mostly citing meddling and hectoring by Washington.

U.S. officials are playing it cool. Joseph Nye Jr., an assistant secretary of defense, surprised a standing-room-only crowd in Pretoria recently when he announced that South Africa’s strategic minerals no longer “matter” to Washington now that the Cold War has ended.

“As we look at Africa . . . we have very little strategic interests and only modest economic interests,” Nye added. Many in the room appeared stunned.