LE BOURGET, France — Less than two days before their deadline to conclude a sweeping new climate accord, negotiators from nearly 200 countries have yet to resolve major issues, such as how and when pledged cuts to carbon emissions would be verified.

Lead negotiators said they were confident that a deal could still be reached — and perhaps in time to meet the Friday deadline. But some outside observers who have been monitoring the talks said that the compromises necessary to bring it across the finish line could weaken the deal so much as to make it nearly toothless.

At the heart of the proposed deal are a set of pledges from 186 countries, representing over 90 percent of the global economy, to cut their emissions. But a draft text published on Wednesday did not include any details on how those emissions cuts would be monitored and verified.

Meanwhile, even if enacted, those pledges would cut emissions about only half as much as necessary to curb greenhouse gases to the level needed to prevent the atmosphere warming by 2 degrees Celsius, or 3.6 degrees Fahrenheit. At that point, scientists say, catastrophic effects would kick in, such as devastating floods, droughts, food shortages and intense storms.