Tesla Inc's top boss Elon Musk said Tesla is tweaking its self-driving software to eliminate a phantom braking problem and may release a significantly improved version within the next two to three weeks.

Tesla shares fell 2.7% to $600.42 in morning trade, headed for a third straight decline. U.S. federal and state regulators have been scrutinizing Tesla's semi-automated driving system following accidents in Texas and other areas.

"I think we're maybe a month or two away from wide beta. But these things are hard to predict accurately," Musk said in a Tweet.

In April, Musk said he would be "surprised" if wide beta service was available later than June, calling a May launch "aspirational."

In October, Tesla rolled out a pilot program of its long-touted beta full self driving (FSD) technology to a limited number of employees and customers, but has delayed the wider launch.

"We had to focus on removing radar & confirming safety," Musk said, referring to its plan to rely on cameras for its system.

When asked by a Twitter user whether its vision-only system would remove the "phantom braking" issue, in which a Tesla car sometimes applies a brake abruptly under an overpass or a bridge, he said, "yes."

In March, Tesla told California regulators that it may not achieve full self-driving technology by the end of this year. It said it is currently offering a driver assistant, level-2 technology that requires driver supervision.

Subscriptions to the software for the system would be offered within a month, Musk said, without elaborating further.