"It does seem that comet ISON probably has not survived its journey," Naval Research Laboratory comet scientist Karl Battams said after looking at space images.
"I am not seeing anything that emerges from behind the solar disk and that I think could be the nail in the coffin," he told a roundtable organized by the US space agency NASA.
The large block of ice and rock had been expected to skim just 730,000 miles (1.17 million kilometers) above the sun's surface around 1830 GMT.
It was estimated that ISON would undergo temperatures of 4,900 degrees Fahrenheit (2,700 Celsius) and lose three million tonnes of its mass per second as it made its journey around the sun. Most astronomers had predicted that ISON would not survive the trip.
Several solar observatories watched the comet during its closest approach to the sun, known as perihelion. The comet became faint while still within view of NASA's Solar Terrestrial Relations Observatory, and the joint European Space Agency and NASA's Solar and Heliospheric Observatory.
NASA's Solar Dynamics Observatory, however, could not see the comet.
ISON was about half the size of an average comet, with an estimated maximum diameter of 0.75 miles (1.2 kilometers).
With agency inputs