A storm moving closer to the US East Coast will deliver tropical storm conditions to North Carolina on Friday before making landfall on Saturday, the National Hurricane Center said.

The storm was off the coast of South Carolina and North Carolina with top sustained winds of 85 kmph. A storm surge watch was in effect, with surges between 0.9 to 1.5 metres forecast for parts of North Carolina, the centre reported.

As of Friday morning, the storm was located about 530km southeast of Charleston, South Carolina, and about 525km south Cape Hatteras, North Carolina, and moving north at around 22kmph, the centre said.