(Adds quotes from State Department, White House, U.N.)
WASHINGTON, June 24 (Reuters) - The international community will reject any attempt by Zimbabwean President Robert Mugabe to declare himself president if he goes ahead with a planned run-off election, the U.S. State Department said on Tuesday.
"If the election takes place and Mugabe stands up there and declares himself president again on the basis of that, I think it’s going to be uniformly rejected by the international community," State Department spokesman Tom Casey said as pressure mounted to call off Friday’s poll, from which the opposition candidate Morgan Tsvangirai has withdrawn.
Casey pointed to pressure from Zimbabwe’s African neighbors and the U.N. Security Council’s unanimous condemnation of violence against Tsvangirai’s supporters, that won rare backing from South Africa, China and Russia, who have previously blocked such moves.
Mugabe, who has held uninterrupted power for 28 years, on Tuesday defied mounting pressure from inside and outside Africa, including Monday’s council statement, to call off the vote, saying he had a legal obligation to go ahead.
But Casey said "there will be consequences for Zimbabwe as a whole if it, in effect, has a government that no one views as having any credibility."
Asked what concrete steps the United States would take if Mugabe pushed ahead with the vote, he said Washington would monitor the impact of the U.N. and regional pressure campaign, but had room to impose firmer measures, if needed.
"We have an extensive series of targeted sanctions against President Mugabe and the regime," Casey said.
"That, by no means, is the limits of what the U.S. can do bilaterally. It certainly is by no means the limits of what other members of the international community could do and might do in response to this," he added.
At the United Nations, U.S. Ambassador Zalmay Khalilzad said the council will consider further steps on Zimbabwe if Harare ignores the statement.
"We will look at measures to be taken in the face of the defiance," Khalilzad said. "We don’t have any specific date or measure at this point in mind ... We have to give it a little bit of time to see what the reaction is, and then we have to look at what do you do to bring about compliance."
White House spokeswoman Dana Perino said "We already think that it’s an illegitimate government" because Tsvangirai’s Movement for Democratic Change had won the first round of the election on March 29. She said Tsvangirai had agreed to the run-off in order to adhere to the Zimbabwe constitution. (Reporting by Paul Eckert, Matt Spetalnick and Patrick Worsnip at the United Nations)