HARARE, Zimbabwe (CNN) -- Zimbabwe dispatched artillery, soldiers and armed personnel carriers to Congo on Thursday, apparently to help the embattled president rout rebels in the country's eastern jungles.

The deployment came a day after Zimbabwe joined two other South African countries, Namibia and Angola, in announcing plans for a major offensive in eastern Congo. To date, their forces were concentrated in western Congo, where they fended off a rebel advance in August.

The joint military campaign against the rebels threatens to turn into a major escalation of a conflict that already has embroiled Rwanda and Uganda, which reportedly back rebels trying to topple Congo President Laurent Kabila.

Howard Wolpe, President Clinton's envoy to the region, called for restraint.

"We are anxious to get a cease-fire in place. ... We do not want to see the situation there get out of control," Wolpe said after meeting Zimbabwe President Robert Mugabe on Thursday.

Fighting in steamy, insect-infested jungles familiar to the rebels could be difficult.

Seasonal rains that close many roads are imminent. Low cloud cover and tropical rainfall would also curtail the allies' advantage of air power, said Harare-based defense analyst Michael Quintana.

The rebels "are likely to roll with the allied punch, bide their time and then come back with a sting," he said.

Residents on the main route to Harare's Manyame military air base reported seeing convoys of troops, munitions, armored cars and trucks towing artillery headed toward the base Thursday.

Military transport airplanes were seen taking off, witnesses said.

There was no official word on how many reinforcements were on their way to join about 3,000 Zimbabwe troops already in the Congo, formerly Zaire.

"We are working in line with what the heads of government decided yesterday," said Col. Chancellor Diye, spokesman for the Zimbabwe National Army. He would not elaborate.

Also Thursday, Rwanda's vice president, Gen. Paul Kagame, met with South African President Nelson Mandela in Pretoria, South Africa's capital. No details of their discussions were released.

Mandela is trying to broker a peace accord for Congo.

In New York, meanwhile, the U.N. Security Council called for an immediate end to military offensives in Congo. The Security Council expressed support for efforts by the Organization of African Unity and regional groups to arrange a cease-fire and urged all parties to attend October 26 talks in Zambia aimed at resolving the crisis.

Security Council President Sir Jeremy Greenstock of Great Britain read to reporters a statement written by the council urging defense ministers from the various countries involved in the conflict to attend the meeting in Zambia.

"Use this major opportunity in a spirit of realism and compromise to bring a destructive cycle of violence in the region to an end," the statement said.

Also in the statement were details of the Security Council meeting. "Council members called for an immediate end to military offensives and hostilities generally, and for respect for the sovereignty and territorial integrity of the Democratic Republic of the Congo," the statement said.

The Associated Press and Reuters contributed to this report.