By Sue Pleming

PRETORIA (Reuters) - U.S. Secretary of State Hillary Clinton encouraged South Africa on Friday to press for reform in Zimbabwe and said Washington would build closer ties with Pretoria after strains under the Bush administration.

Before meeting South Africa's foreign minister on Friday, Clinton said she would urge the new government to get Zimbabwe to raise the pace of political reform which has been too slow for donors to release substantial amounts of aid.

"South Africa is very aware of the challenges posed by the political crisis in Zimbabwe because South Africa has 3 million refugees from Zimbabwe," Clinton told a news conference after meeting International Relations and Cooperation Minister Maite Nkoana-Mashabane.

"And every one of those refugees represents a failure of the Zimbabwean government to care for its own people and a burden that South Africa has to bear," she added.

The United States, troubled by what it sees as an absence of reform in Zimbabwe, has no plans either to offer major development aid or to lift sanctions against Mugabe and some of his supporters.

"Now we as you know are attempting to target the leadership of Zimbabwe with sanctions that we think might influence their behavior without hurting the people of Zimbabwe," said Clinton.

Before sanctions can be lifted or major aid can flow, Washington wants more evidence of political, social and economic reforms by Mugabe and the government he shares with opposition leader and now Prime Minister Morgan Tsvangirai.

Mugabe, in power since independence from Britain in 1980, is blamed for plunging Zimbabwe into economic ruin. He argues that his country's economic woes, which include hyperinflation and a collapsed infrastructure, are caused by sanctions.

New South African President Jacob Zuma, due to meet Clinton in the coastal city of Durban on Saturday, has taken a harder line on Zimbabwe than his predecessor Thabo Mbeki, but the United States wants more.

GOODWILL

Clinton hopes there will be a burst of goodwill due to the change of government in both South Africa and the United States and that it will lead to better relations with Pretoria than the Bush administration had.

"I know that the (foreign) minister and I are interested in making sure that our two countries not only lead but demonstrate the kind of cooperation that results in positive results for the people of the world," said Clinton.

Nkoana-Mashabane said coordination with the previous U.S. administration had been poor and she wanted to "elevate" the relationship with the Obama team. She also promised South Africa would try to get Zimbabwe to move faster in introducing reforms.

A senior U.S. official said earlier that "U.S.-South African relations were not as warm and friendly in reality as many people thought" when President Thabo Mbeki was in power.

The United States had disagreed, for example, with Mbeki's questioning of established scientific understanding of HIV/AIDS.

Walter Kansteiner, a top Africa diplomat for the Bush administration, said Clinton should work Zuma "very hard" on Zimbabwe and follow up with him after their meetings.

"I think we left Pretoria off the hook too many times on Zimbabwe ... but in our defense there were a lot of other issues on our agenda and the feeling was, why jeopardize all these many other things?" he said.

Later, in a speech to business leaders in nearby Johannesburg, Clinton urged closer trading ties and spoke of plans for a U.S.-South Africa business council.

Clinton pushed for greater trade with the United States and urged South Africa to trade more with other African nations.

"South Africa will not fulfill its economic potential if it exists as an island of relative prosperity amid a sea of untapped opportunity elsewhere on the continent," she said.

Clinton, on an 11-day trip to Africa, also met former South African president Nelson Mandela at his foundation in Johannesburg, and was given a tour of his personal archives.

(Writing by Sue Pleming and Michael Georgy; editing by Sonya Hepinstall)