Democratic U.S. senators are urging President Barack Obama to pursue a global climate agreement that requires both industrialized and developing nations to cut emissions.

Nine senators sent a letter to the president Thursday, stressing the need for an effective global response to the threat of climate change.

The lawmakers said engaging the developing world will be especially important. They said developing nations represent half of global emissions and are expected to account for nearly all growth in future emissions.

The senators warned against "poorly designed climate policies," which they said could jeopardize U.S. national interests by imposing burdens on consumers, companies and workers.

The senators who signed the letter include Arlen Specter of Pennsylvania, Carl Levin of Michigan and Claire McCaskill of Missouri.

Their appeal comes just days before world leaders unite in Copenhagen for a United Nations summit on climate change.

The senators who signed the letter said the United States should negotiate international climate agreements that promote cost-effective action and reciprocal commitments.

They said an international agreement should give priority to verifying that nations are meeting their commitments and include appropriate consequences for those that are not.

Lawmakers have expressed concern that U.S. action, without commitments from rising economic powers like China and India, would barely dent the problem and lead to energy cost increases and lost jobs in the U.S.