African climate negotiators attending the U.S.-Africa Leaders Summit in Washington this week said leadership from the United States is critical to finalizing a global deal on measures to address climate change in 2015 after years of deadlock.

Officials from Tanzania, the Democratic Republic of Congo, Ghana and Ethiopia said they were optimistic an agreement could be reached, even though many U.S. lawmakers, particularly Republicans, oppose signing a binding treaty requiring cuts in greenhouse gas emissions.

Without leadership from the United States, China - the world's biggest producer of greenhouse gases - will be reluctant to act, putting at risk developing countries directly affected by climate change, one negotiator told a small group of reporters convened by the World Resources Institute (WRI), an environmental research group.

"As an African, there are no clean emissions or dirty emissions. Whether they emissions are from China, emissions from the United States ... that doesn't keep me safe as an African," said Tosi Mpanu-Mpanu, lead negotiator for the Democratic Republic of the Congo.

"We have a saying that when two elephants fight, the grass suffers. We don't want to be the grass under the U.S. and China," he said.

Jennifer Morgan, director of the climate program at WRI, said African countries are among the most vulnerable to the impacts of climate change, such as more severe weather, but contribute just 3 percent of global greenhouse gas emissions.

Negotiating countries hope to ink a global pact to replace the 1997 Kyoto Protocol, but have long argued over how the costs of cutting greenhouse gases should be distributed among rich and poor nations.

At the 2013 U.N. Climate Change Conference in Warsaw, African countries floated a proposed an "equity reference framework" to shape a climate agreement that avoids the so-called firewall between developed and developing countries.

The proposal, which the bloc is likely to re-introduce at talks in Lima, Peru in December, seeks to address historical and current contributions to emissions.