(Adds Conoco CEO quote, paragraphs 6-7)
MOSCOW/LONDON, May 13 (Reuters) - Around a dozen chief executives and chairmen of major U.S. and European corporations have withdrawn from an economic conference in Russia as pressure between Moscow and the West grows over the crisis in Ukraine.
Eleven business leaders who were listed in late March as scheduled to attend the May 22-24 St. Petersburg International Economic Forum are no longer on the forum's website.
Only one company said their executive's decision to stay away was because of political tensions with most declining to give a reason. The cancellations, however, coincide with the United States and Europe considering further sanctions on Moscow over violence in eastern Ukraine, which western governments have blamed in part on Russia.
Sanctions have already been imposed in reaction to Russia's annexation of Crimea.
The chief executives of oil producer ConocoPhillips, jet maker Airbus Group, Visa Inc, Aluminium group Alcoa, Siemens, Citigroup, Morgan Stanley, International Paper Company, Pepsi , Italian oil group Eni and the chairman of consulting group Bain & Company are among those no longer scheduled to attend the forum.
Ryan Lance, the chief executive of Conoco, said he decided not to attend after discussions with the U.S. government.
"Like many of the American CEOs and industry leaders, we were approached by the State Department and talked to about many of the concerns that they had," Lance told reporters after the company's annual meeting on Tuesday. "So based on some of those concerns and comments I made a decision to not attend this year."
More than a dozen Western business leaders, including Goldman Sachs Chief Executive Lloyd Blankfein, remain on the programme but sources close to some of the companies said other bosses planned to pull out. Goldman declined comment.
White House spokesman Jay Carney said this month that U.S. officials had been discussing the event, Russia's answer to the Davos World Economic Forum, with business leaders, and had made it clear that attending would not be appropriate given "flagrant violations of a sovereign nation's territorial integrity."
Business sources said the withdrawal of CEOs from the forum, which is held "under the auspices" of the president, according to its website, could be considered as a sleight by Russian President Vladimir Putin and could damage their companies' businesses in Russia.
"I am sure that the forum will be held in a friendly atmosphere and that any withdrawals will not spoil the atmosphere," said Deputy Minister of Economic Development Sergey Belyakov in a video interview posted on the forum's website.
"Many companies confirmed their participation and we have no problems with the quality of our participants or of the number. Around 6,000 participants confirmed - many top managers of Russian and foreign companies that are in Forbes and Fortune ratings," Belyakov said.
"I am surprised at the pressure coming from the White House administration. The only parties which will suffer will be American companies."
Belyakov said Russia understands the atmosphere in which American companies are making their decisions and said there would be no risks for those companies in Russia who cancel.
Representatives of Pepsi, Citigroup and Siemens confirmed their bosses had withdrawn, and blamed scheduling clashes. Representatives of Airbus, Visa, Morgan Stanley, International Paper, Bain & Company, declined comment or were not available for comment.
(Additional reporting by Tim Hepher in Paris, Jens Hack in Frankfurt, Lisa Baertlein in Los Angeles, Anna Driver in Houston, Lauren LaCapra, David Henry, Ernest Schneyder and Lewis Krauskopf in New York, Ludmila Danilova in Moscow; Editing by Anna Willard and Grant McCool)