The United States Wednesday called the arrest of Zimbabwean opposition leader Morgan Tsvangerai deeply disturbing and urged his immediate release. U.S. officials want Zimbabwe's neighbors, especially South Africa, to use more leverage on Harare authorities to assure a free and fair presidential runoff election June 27. VOA's David Gollust reports from the State Department.

The State Department is calling Mr. Tsvangirai's latest detention "extremely disturbing news" and it is demanding that Zimbabwean authorities release him immediately and "unharmed and untouched" - mindful that he was badly beaten in police custody last year.

Bush administration officials are increasingly pessimistic that the June 27 runoff, pitting President Robert Mugabe against Mr. Tsvangerai, will meet international standards.

But for now, the United States is pressing diplomatically for international pressure on the Mugabe government to allow a free and fair campaign and vote.

Briefing reporters, State Department Spokesman Sean McCormack acknowledged there is little the United States can do, having already imposed travel and financial sanctions targeted at President Mugabe and his inner circle.

He said hopes for prodding the Harare government into positive action rest with the country's neighbors and especially South Africa where President Thabo Mbeki and his African National Congress have longtime links with President Mugabe and his ZANU-PF party.

"States like South Africa, for example, need to use the leverage that they have. It is a tragic situation," said McCormack. "This is a state that was once a model for southern Africa. It was a net exporter of food, it was a proud state that emerged from a colonial past. And the rule of one man and his party has really destroyed the economy of the state and really destroyed any tradition of democracy in Zimbabwe."

McCormack said U.S. diplomatic appeals to South Africa on Zimbabwe have been made "top-to-bottom," including calls by Secretary of State Condoleezza Rice to President Mbeki.

A State Department official said a priority for U.S. officials in recent days has been to try to get South Africa and other neighboring countries to send more election observers to Zimbabwe than they did for the first round of presidential voting March 29.

McCormack, meanwhile, reiterated U.S. concern about the Mugabe government's decision to expel CARE international and other aid groups amid charges they were aiding the Tsvangirai campaign.

He said it is exactly the wrong thing to do at a time of an emerging food crisis to, as he put it, "cut off the lifeline" of support for the more than 100,000 Zimbabweans who depend on the outside aid.