Countries that have adopted sanctions already need to implement them robustly.
Cameron said Europe listened to British expertise on how to implement sanctions, and said the level of sanctions "might become materially different" in the future.
Speaking at a news conference before the meeting of nations professing nonalignment that opens here on Monday, Mr. Mugabe said that although his Government had again signed a special trade agreement with South Africa, the "decision to implement sanctions will override that agreement" once the sanctions agreed to by Commonwealth countries were in place.
The administration has had some success getting Russia, Iran's longtime enabler, to implement sanctions.
But last December AIPAC's efforts to implement sanctions against Iran were so intense that even this well-tempered partnership fractured.
Early in the administration, Mr. Fuerth used his perch as head of an interagency process to implement sanctions against Haiti, Serbia and Iraq.
The banks' offer came two weeks before states including New York, New Jersey, Florida and California were about to implement sanctions against the banks over the affair.
The Trump White House has also been slow to implement sanctions against Russia passed overwhelmingly by Congress in response to election meddling.
Yet another potentially crippling sanction against Iran moved a step closer on Friday when the Belgium-based Society for Worldwide Interbank Financial Telecommunication, known as Swift, said in a statement on its Web site that it was "ready to implement sanctions against Iranian financial institutions".
But Gregor Reiter of the European Football Agents Association admitted that sanctions have been hard to implement due to different rules being adopted around the continent.
"We will also be making sure the FDA looks into the matter because they are the regulatory body with the power to implement sanctions, such as fines," Calibo added.
