Some new bad news for Yahoo. Ten days after the troubled web portal announced it will lay off 1,500 employees, the Wall Street Journal reported Thursday that Yahoo’s deal with Google is on shaky ground.

The Journal said that both Google (GOOG) and Yahoo (YHOO) may walk away from the ad search agreement next week because the Justice Department has been moving toward a suit to block the deal. That would be a big blow to Yahoo, which was banking on making as much as $800 million in annual revenues by outsourcing some search ads on its web properties to Google.

In a statement, Yahoo representative Adam Grossberg said the discussions with the feds are “on going.”

Google representative Adam Kovacevich said in a statement that the company is “continuing to have cooperative discussions with the Department of Justice about this arrangement, and agreed to a brief delay in implementing the agreement while those discussions continue.”

Confidence in the deal is waning. In mid-June, Google and Yahoo originally said they would give the feds 100 days to review the ad pact before moving forward with the agreement. But the pair have faced an uphill battle in Washington. In early August, Yahoo filed a heavily redacted version of the deal to the Securities and Exchange Commission. Then Google CEO Eric Schmidt told reporters that he planned to go ahead with the partnership in mid-October with or without approval from the Justice Department. So far, the feds have yet to give the Internet frenemies the green light.

Critics say the ad pact would give Google too much power and make search advertising less competitive. Google currently owns 62% of the U.S. search market, according to comScore’s monthly figures for September. Yahoo is second with a 20% share and has lost 20% of its search share to Google in the past 18 months.

A source familiar with Google’s thinking said no decision has been made. Some analysts have already moved on even if the feds haven’t.

On Wednesday, J.P. Morgan Internet analyst Imran Khan sent a note to clients on why Yahoo should forget about the Google deal and sell its search business to Microsoft (MSFT). Khan suggests that Yahoo can gain an additional $725 million in operating cash flow from outsourcing search to Microsoft. The software company had offered Yahoo a reported $2 billion to buy its search business after talks to acquire all of Yahoo failed.

Writes Khan, “We think that it is unlikely that the Google/Yahoo search partnership will pass DOJ review in its current form….Without its search business, Yahoo would be very clearly positioned as a content and display advertising entity, thereby clarifying and defining its purpose to advertisers and users.”