* Casino stocks dip, while gunmakers rise after Las Vegas shooting
Citrix Systems top stock on the S&P 500
* Indexes up: Dow 0.22 pct, S&P 0.10 pct, Nasdaq 0.2 pct (Updates to open)
By Ankur Banerjee
Oct 2 (Reuters) - All the three major U.S. stock indexes opened at record highs on Monday, the first trading day of the fourth quarter, as investors bet on President Donald Trump's tax reform plan making some headway.
Shares of Casino operators MGM Resorts International , Melco Resorts & Entertainment, Wynn Resorts and Las Vegas Sands slipped after a gunman killed at least 50 people in Las Vegas on Sunday.
Gunmakers Sturm Ruger & Co and American Outdoor Brands moved higher after the mass shooting at a country music festival.
Investors, however, focused on Trump's tax reform.
"The market is optimistic today, hoping that some kind of tax reform package will be discussed at Washington," said Robert Pavlik, chief market strategist at Boston Private in Fairfield, Connecticut.
"Investors are also beginning to position themselves for the earnings season and the fourth quarter."
Trump has called for tax cuts for most Americans in his proposal, but has drawn criticism that the plan favors business and the rich and could add trillions of dollars to the deficit.
Despite inflation remaining below the 2 percent target set by the Federal Reserve, Fed Chair Janet Yellen's recent speech has suggested the odds of an interest rate hike in December remain high.
Trump has promised a decision this month on who is likely to be the new chief of the U.S. central bank and has met with former Federal Reserve Governor Kevin Warsh and three others.
President Trump would soon have to announce who would chair the Fed and many do think that he may favor someone who would take a more aggressive approach towards monetary policy, said Naeem Aslam, chief market analyst at ThinkMarkets UK.
U.S. stocks are at record levels, with each of the major indexes ending the third quarter with solid gains on Friday.
Nine of the 11 major S&P indexes were positive on Monday, led by healthcare and technology sectors.
Oil fell more than $1 a barrel to below $56 on Monday as a rise in U.S. drilling and higher OPEC output put the brakes on a rally that helped prices to register their biggest third-quarter gain in 13 years.
Federal Reserve Bank of Dallas President Robert Kaplan scheduled to participate in a moderated Q&A session hosted by the Dallas Federal Reserve at 2:00 p.m ET.
At 9:48 a.m. EDT the Dow Jones industrial average was up 49.02 points, or 0.22 percent, at 22,454.11, the S&P 500 was up 2.55 points, or 0.10 percent, at 2,521.91 and the Nasdaq Composite was up 12.72 points, or 0.2 percent, at 6,508.68.
General Motors was up 3.3 percent in early trading.
Shares of Nordstrom fell 5 percent following a New York Post report that talks to take the department store operator private were faltering.
Citrix Systems was the top stock on the S&P 500, up 3.6 percent after Wells Fargo upgraded the cloud-computing company to "outperform".
Advancing issues outnumbered decliners on the NYSE by 1,417 to 1,224. On the Nasdaq, 1,476 issues rose and 1,010 fell. (Reporting by Ankur Banerjee and Yashaswini Swamynathan in Bengaluru; Editing by Sriraj Kalluvila)