By Trevor Hunnicutt WASHINGTON (Reuters) – The White House is refusing to negotiate with hardline Republicans on raising the debt ceiling because it believes enough of them will eventually back off their demands, as a growing chorus of investors, business groups and moderate conservatives warn of the dangers of edging towards a default. The high-stakes deadlock is widely expected to last for months, and could come down to the last minute as each side tests the other ahead of June when the U.S. government might be forced to default on paying its debt. As the White House calls for House of Repre…