A weakened United States could start retreating from the world stage without help from its allies abroad, an international strategic affairs think tank said Tuesday.
The London-based International Institute for Strategic Studies said President Barack Obama would increasingly turn to others for help dealing with the world's problems — in part because he has no alternative.
"Domestically Obama may have campaigned on the theme 'yes we can'; internationally he may increasingly have to argue 'no we can't'," the institute said in its annual review of world affairs.
The report said the U.S. struggles against insurgent groups in Iraq and Afghanistan had exposed the limits of the country's military muscle, while the near-collapse of the world financial markets had sapped the economic base on which that muscle relied.
The report also claimed that the United States had lost traction in its efforts to contain Iran's nuclear program and bring peace to the Middle East.
"Clearly the U.S. share of 'global power,' however measured, is in decline," the report said.
The report praised the U.S. president, saying that he recognized there was only so much America could do "to impose its views on others."
After years of often thorny relationships between the United States and its allies during President George W. Bush's administration, Obama has talked of the need to work with other nations on such issues as the financial meltdown, climate change and nuclear proliferation.
"These are challenges that no single nation, no matter how powerful, can confront alone," Obama said in April after attending the G-20 summit in London.
"The United States must lead the way," he said. "But our best chance to solve these unprecedented problems comes from acting in concert with other nations."
The think tank's report said Obama could help restore the United States' standing by working with its friends abroad to contain emerging threats to its position as the world's pre-eminent power.
Controlling the nuclear ambitions of Iran and North Korea would require help from regional allies, the report said.
The same was true of Afghanistan, where the United States has had difficulty persuading its NATO partners to follow its lead in boosting the number of troops it has sent to fight a resurgent Taliban.
"In the next year or two, the greatest demand on U.S. talents and power will be to persuade more to become like minded and adopt greater burdens," the report said.