By Mike Stone WASHINGTON (Reuters) – President Joe Biden is expected to ask Congress for more than $770 billion for his U.S. defense budget for the next fiscal year as the Pentagon seeks to modernize the military, according to three sources familiar with the negotiations, eclipsing the record budget requests by former President Donald Trump. Ongoing budget talks between Defense Secretary Lloyd Austin and the White House’s Office of Management and Budget (OMB) have coalesced around a proposed national defense request of higher than $770 billion for the 2023 fiscal year starting Oct. 1, the sour…