
Aviation and shipping look set to be included in a government bill targeting cuts in greenhouse gases, to head off a rebellion by backbench MPs.
MPs will vote later on a bill to enforce an 80% reduction in carbon emissions by 2050.
More than 50 Labour MPs have backed an amendment calling for the law to cover emissions from planes and tankers.
Ministers said the bill would "take into account" the two sectors, a move welcomed by environmental campaigners.
But it is unclear what this will mean in practice and whether ministers will back the rebel amendment, signed by 56 MPs, seeking statutory rather than voluntary targets for aviation and shipping.
The amendment seeks equivalent cuts in emissions elsewhere to make up for any rise in those from the two industries.
The government has resisted calls in the past for such a move, arguing it would be difficult to determine how international aviation and shipping emissions could be allocated between different countries.
But earlier this month, the new climate change secretary Ed Miliband said he would accept recommendations from the government's advisory committee on climate change, headed by Lord Turner, that the sectors must figure in climate change targets.
In a statement ahead of Tuesday's vote, officials said they were "determined that international aviation and shipping should be part of a comprehensive approach for tackling climate change".
"We want to reflect Adair Turner's advice to government that emissions from aviation and shipping should be taken into account when developing our strategy to reach our targets," they said.
But they added that there must also be a recognition that "there is currently no agreed method of allocating international emissions to individual countries".
Environmental campaigners said such a commitment would make the legislation much more effective.
"The final piece of the jigsaw is in place," said Andy Atkins, of Friends of the Earth.
"People from right around the UK demanded a strong law. The government have listened."
Green Party leader Caroline Lucas said such a move would signal that ministers were "starting to take their environmental responsibilities seriously".
But she said the government's current emissions record was poor and that it needed to prevent future airport expansion around London if it was to be serious about meeting its targets.
The Climate Change Bill, being given its third reading in the Commons, would require the government to publish carbon budgets every five years and enable it to set up carbon trading schemes.