Updated

US diplomats and lobbyists are stepping up pressure to reduce African commercial ties to Iran as part of a growing global push to squeeze Tehran, an effort that already led several African companies to consider leaving the country.

Among the results so far, Angola's state-owned energy company, Sonangol, is considering pulling out of an Iranian gas deal, and Sasol of South Africa says it is discussing whether to divest itself of its 50 percent share in a $900 million Iranian petrochemical project.

The moves come as the US and European Union continue to expand sanctions and try to persuade consumers of Iranian oil to find alternative supplies to choke off Tehran's revenue and force it to abandon what the West says is a program to develop nuclear weapons, a charge Iran denies.

US officials visited China, Japan and South Korea this month to ask them to reduce crude purchases from Iran. Many US and European companies that did business in Iran through subsidiaries already backed out amid an expanding sanctions regime

African companies were among those entering Iran as Western giants pull out. Meanwhile, Iranian exports, largely oil, to sub-Saharan Africa rose to $3.60 billion in 2010 from $1.36 billion in 2003, according to the International Monetary Fund. In addition to its ties with Angola and South Africa, Iran has pledged investments in Uganda, Ghana and Senegal, though not all have materialized.

Now, African countries that once were viewed as distant from the conflict with Iran are getting drawn into the sanctions effort.

US deputy secretary of energy Daniel Poneman in the past week discussed with South Africa's minister of energy ways that Pretoria might replace Iranian oil imports with other sources of supply. South Africa relies on Iranian oil for about one-quarter of its imports.

US government representatives also have met with private companies in South Africa to discuss Iran sanctions, a US spokeswoman said.

Click here to read more on this story from The Wall Street Journal.