AMSTERDAM – The United States assured international negotiators Monday it remains committed to reducing carbon emissions over the next 10 years, despite the collapse of efforts to legislate a climate bill.

U.S. delegate Jonathan Pershing told a climate conference in Bonn, Germany, Washington is not backing away from President Barack Obama's pledge to cut emissions 17 percent from 2005 levels.

Pershing said legislation is the preferred way to control greenhouse gases, but the administration "will use all the tools available" to reach its target.

Obama made the pledge at a climate summit in Copenhagen last December, and affirmed it in a formal note to the U.N. climate secretariat. At the time, the U.S. House of Representatives had passed a climate bill and the Senate had been broadly expected to follow suit.

But the withdrawal of a scaled down climate bill last week in the Senate raised concern about America's commitment to fight global warming and disappointed developing countries that had hoped Obama would seize international leadership on the issue.

The European Union said the failure of the bill encumbered its talks among its own 27 member states on whether the EU should increase its pledge to rein in the gases blamed for global warming.

"It hasn't made the discussion and the debate any easier in Europe," Artur Runge-Metzger, the European Commissioner for climate change.

The EU has promised to cut emissions by 20 percent below 1990 over the next decade, but said it would raise its target to 30 percent if the U.S. and other major polluters adopt similarly tough goals.

Delegations from 178 countries began five days of work Monday, resuming painstaking discussions on an agreement to limit global emissions and prepare poor countries for the effects of a warming world.

Delegates pointed to the lethal floods in Pakistan as an example of a the extreme weather events that scientists say will become more common as average temperatures rise.

As if to underscore the global warming threat, U.N. officials lifted the coat-and-tie rules for the week, citing soaring temperatures in Bonn and a desire to lower the air conditioning to reduce the conference's emissions.

One more round of talks is scheduled in Tianjin, China, in October before the next major climate conference Nov. 29-Dec 10 in Cancun, Mexico.

Acknowledging widespread concern over the U.S. position, Pershing said many delegates had asked him about the status of its pledge and the chances of a deal in Cancun.

"Success in Cancun does not hinge on U.S. legislation," he told some 3,000 delegates, businessmen and activists attending the talks.

Environmental groups warned that the setback in Washington should not deter other countries, and called on the EU to take the lead.

"Parties should not allow U.S. domestic politics to lower the overall level of ambition of an international agreement," said Manuel Oliva, of Conservation International.

A study by World Resources Institute said the Obama administration could reach the 17 percent goal without passing a sweeping climate bill by using existing powers, including those of the Environmental Protection Agency; by issuing new regulations and executive orders; and through piecemeal energy legislation, Oliva said.

The talks in Bonn and Tianjin aim to prepare a successor agreement to the 1997 Kyoto Protocol, which calls on industrial countries to reduce emissions but makes no demands of developing countries like China and India, which are now among the largest polluters.

The United States rejected Kyoto as imbalanced and unfair, but said it will join a new climate regime as long as it is "symmetrical," encompassing all major emitters.

The emissions-controlling terms of the Kyoto accord expire in 2012, a deadline that has delegates worried about leaving a vacuum unless a new agreement is in place — the so-called Kyoto gap.

Negotiations have stumbled along for 2 1/2 years. The original intention was to seal an agreement in Copenhagen, but that summit of 120 world leaders in the Danish capital only managed to agree on a brief political statement of intentions.

The top U.N. climate official, Christiana Figueres, said it may be unnecessary to complete a full agreement in Cancun. It was up to the countries to decide whether they want to make it legally binding or a series of less enforceable decisions.

But she said by the Cancun conference begins wealthy countries should have made the first payment of a $30 billion three-year promise of emergency climate funds to poor countries.

"Developing nations see the allocation of this money as a critical signal that industrialized nations are committed to progress in the broader negotiations," said Figueres.