President Barack Obama has been on the phone, speaking with the leaders of Indonesia, Saudi Arabia, the Philippines and Argentina.
Obama called the leaders to discuss working together on the world's economic crisis, among other issues.
The White House says Obama's conversation with the president of Indonesia also touched on education, health care, climate change, counterterrorism and bird flu.
In his conversation with Philippine President Gloria Macapagal Arroyo, Obama commended her country's efforts against terrorism and in modernizing the armed forces.
Obama will see three of those leaders -- from Indonesia, Saudi Arabia and Argentina -- at the Group of 20 nations summit next month in London.
At the end of his European trip, Obama is scheduled to visit Turkey, a Muslim country where relations with the U.S. were strained by the 2003 invasion of Iraq.