South Africa's main labour federation on Wednesday threatened to blockade a border crossing with Zimbabwe after President Robert Mugabe's government deported a union fact-finding team accused of aiding his enemies.
Officials with the Congress of South African Trade Unions (COSATU) said they would launch an international campaign of protest over Tuesday's expulsion, which saw 13 South African unionists hustled across the border in the dead of night.
"We will do everything, including blocking that bridge where they dumped our delegates," COSATU Secretary General Zwelinzima Vavi told South African national television.
Senior South African officials conceded Zimbabwe's move against COSATU - a key ally of South African President Thabo Mbeki's ruling African National Congress (ANC) - may complicate Mbeki's policy of "quiet diplomacy" toward his northern neighbour.
"Our diplomats are looking into the matter and we can only consider a reaction once we know what precipitated this drastic step. We still take the view that the matter could have been handled in a better way," South African Defence Minister Mosiuoa Lekota said in parliament on Wednesday.
Lekota added that COSATU's expulsion was "clearly a bit embarrassing" for the ANC, which considers the union group an official political partner.
Zimbabwe ordered the COSATU team deported on Tuesday, one day after they arrived in Harare in defiance of a government ban, and police eventually bussed them across the northern border at Beitbridge early on Wednesday after they were unable to catch an airplane at Harare.
The night-time deportation came despite an order from Zimbabwe's High Court which allowed them to stay until Wednesday in order to take a plane.
"We managed to get a court order to the effect that the deportations were illegal but it clearly made no difference. They were escorted by police to the border," COSATU spokesman Patrick Craven said.
The South African delegation, invited by the Zimbabwe Council of Trade Unions (ZCTU), had hoped to meet government and ruling party members and also rights' groups critical of Mugabe on what it described as a mission aimed at helping neighbouring Zimbabwe resolve its political and economic crises.
In a sharply worded statement on Tuesday, Zimbabwe's cabinet accused the COSATU group of working with former colonial ruler Britain to undermine Zimbabwe's sovereignty.