According to Reuters, General Motors said on Wednesday that it was considering extending a 24-hour test drive program that has helped lift US new-vehicle sales in June above expectations.

Gary Cowger, president of GM North America, reportedly said June sales were running at a seasonally adjusted annual rate of about 16.5 million vehicles, including heavy trucks, slightly above May's levels and about flat with last year.

"From where we're at, the month looks OK," he told reporters after the dedication of a new GM engineering building in Warren, Michigan. "We're well ahead of what our expectation was."

However, according to Reuters, he said GM will have difficulty hitting last June's market share level of about 29.3&, one of the strongest months for GM last year.

"It'll be really tough to match that," Cowger reportedly said. "We're going to have pretty strong volume," he added.

So far, Reuters noted, GM has claimed a US market share of about 27.3%.

In April, GM introduced its 24-hour test drive programme, allowing consumers to drive home a GM vehicle overnight before deciding whether to buy, Reuters added.

Cowger told the news agency the programme is gaining momentum and GM is seriously considering extending it beyond the end of July, when he said it is scheduled to end.

"It looks to me like, the longer it's out there, the more people hear about it, the more people are exposed to it, the better job it's doing for us," he said, according to Reuters.