Japan's position as top trading partner with South Africa is causing Foreign Ministry officials embarrassment and prompting accusations that Japan is filling the trade vacuum left by U.S. firms, which have withdrawn from the country. Japan enforces a number of restrictions on links with South Africa, but the trade figures keep growing. According to official figures, Japan became South Africa's No. 1 trading partner in 1986, edging out the United States with two-way trade amounting to $3.59 billion. The estimated trade total for last year is $4.27 billion, a sharp rise even allowing for exchange rate fluctuations.