The Dow Jones industrial average rose as much as 96 points just before 1 p.m., but doubts about the bill cast a shadow over the market as hardline conservatives said they didn't support it. Health care stocks turned lower.

NEW YORK After a promising start, U.S. stock indexes gave up an early rally and ended mostly lower Thursday after Republicans delayed a vote on their health care bill and left investors concerned about delays for the business-friendly agenda of President Donald Trump.

The Dow Jones industrial average rose as much as 96 points just before 1 p.m., but doubts about the bill cast a shadow over the market as hardline conservatives said they didn't support it. Health care stocks turned lower.

Elsewhere, a growing boycott of YouTube advertising hurt Alphabet, Google's parent company. Smaller companies did better than the rest of the market and more stocks rose than fell, a sign investors are still confident in the U.S. economy.

Near the close of trading, House Republican leadership postponed a vote on the American Health Care Act because of a lack of support. Conservatives and more moderate Republicans had opposing concerns about the bill, which is widely disliked by House Democrats.

Jamie Cox, managing partner for Harris Financial Group, said investors are worried about how the Republican-controlled Congress and White House will come together on issues including tax reform, a debt ceiling increase, and a boost in infrastructure spending.

"If the Republicans are having such a difficult time making changes to something they universally agree upon, how on earth are they going to agree on the more complicated tax cut that is coming through later in the year?" Cox asked. Still, the losses were small, suggesting investors think some of those proposals will be delayed rather than abandoned.

The Standard & Poor's 500 index fell 2.49 points, or 0.1 percent, to 2,345.96. The Dow lost 4.72 points to 20,656.58. The Nasdaq composite slid 3.95 points, or 0.1 percent, to 5,817.69. The Russell 2000 index, which tracks smaller companies, gained 7.83 points, or 0.6 percent, to 1,353.43.