President Bush reached out to South African President Thabo Mbeki on Friday as hundreds of guerrilla war veterans in Zimbabwe who support President Robert Mugabe marched through the capital, raising fears Mugabe might turn to violence to prolong his rule.

In a call from Air Force One, Bush sought an assessment of the situation from Mbeki, who is involved in trying to negotiate an agreement between the parties following elections in Zimbabwe. Mugabe’s embattled ZANU-PF party lost control of parliament in weekend elections. The opposition claims to have won the presidency as well, but official returns in that race have not yet been released.

“Our position is to counsel against violence,” White House press secretary Dana Perino said aboard Air Force One en route from Romania to Croatia.

“We believe people should wait for the election results and when the announcement is made, that people respect the outcome,” Perino added.