Experts warn of imminent stock market drop over debt ceiling uncertainty.

The US could breach the debt ceiling as soon as next week, plunging the stock market by nearly half if a protracted default ensues, according to a White House projection. Investors are confident that policymakers will reach a deal on either a comprehensive agreement or a stop-gap measure that averts a debt ceiling breach, market analysts told ABC News. If the White House and Congress fail to make significant progress this week, the uncertainty will put stress on the stock market, they added. A stock market plunge would significantly erode the retirement savings of many Americans, since investors often peg 401(k) accounts to the S&P 500.