Ms Rice declared climate change to be a "real and growing problem" that should be resolved under the UN.
VIDEO: Climate summit
"We have come together today because we agree that climate change is a real and growing problem — and that human beings are contributing to it," Ms Rice says.
"I want to stress that the United States takes climate change very seriously, for we are both a major economy and a major emitter.
“We do not think of ourselves as standing above or apart from the international community on this issue."
The US wants the two-day talks to kick off a 15-month process under which the 16 participating economies will sketch targets for tackling their emissions, examine the possibility of a long-term goal and look at ways of harnessing business and new technology for the carbon cleanup.
The initiative was launched by President George W. Bush, whose country is the world's biggest emitter of greenhouse gases, and who has been savaged abroad for abandoning the UN's Kyoto Protocol in 2001.
His proposal has been clouded by suspicions, especially in Europe, that he wants to undermine efforts to strengthen Kyoto and instead cobble together a voluntary, unambitious deal among an elite club of carbon emitters.
The Washington talks notably take place in the run-up to a key forum in Bali, Indonesia, from December 3-14 on how to deepen emissions cuts after Kyoto's first commitment phase runs out at the end of 2012.
In what seemed a clear attempt to play down the stature of the Washington talks, only six of the invited countries sent a ranking environment minister, with the rest represented only by ambassadors, junior ministers or even a senior official.
Ms Rice, addressing these suspicions indirectly, strived to offer reassurances.
The talks aimed to "ensure that all of us are working pragmatically towards a common purpose, to contribute to a new international framework for addressing climate change beyond Kyoto and to help all nations fulfil their responsibilities under the UN Framework on Climate Change," she says.
Reject mandatory targets
Even so, Mr Bush's rejection of mandatory emissions caps and faith in a voluntary approach to curbing global warming came in for veiled criticism.
"We have actually found many, many countries voicing our view that (a) voluntary approach may be useful but will not solve the issue," says Deputy Environment Minister Humberto Rosa, representing the European Union (EU).
"Voluntary goals so far have not got us to the level of ambition that we need," Mr Rosa says.
He says Europe would insist on getting a clear picture as to how Mr Bush's initiative will interlock with the wider forum of Bali before it agreed to a future agenda and schedule of meetings.
"We look at it (the initiative), and all parties look at it, very constructively," he says.
‘New engagement’ on issue
"There's some new engagement by the US that we love to have, we need US leadership on climate.
"But we want to look into the practicalities of how this will feed (into Bali)," he says, adding: "We don't want to take the risk, even if the intention is not there, of hampering Bali in any way."
The 16 nations gathered in Washington are Australia, Britain, Brazil, Canada, China, France, Germany, India, Indonesia, Italy, Japan, South Korea, Mexico, Russia, South Africa and the United States.
Together they account for about two-thirds of the world's population, 80 percent of the global economy and about 80 percent of global emissions, noted Ms Rice.