(Reuters) - Wall Street's main indexes were mixed at the start of a holiday-shortened week on Monday, after a stopgap government funding bill averted a partial shutdown and investors braced for a slower pace of rate cuts from the U.S. central bank next year.

The United States Congress passed spending legislation early on Saturday, minutes after the funding expired, which could have disrupted everything from law enforcement to national parks ahead of the busy Christmas travel season.

At 09:45 am ET, the Dow Jones Industrial Average fell 132.48 points, or 0.32%, to 42,704.92, the S&P 500 gained 1.04 points, or 0.01%, to 5,931.36, and the Nasdaq Composite gained 57.63 points, or 0.31%, to 19,630.23.

Most heavyweight megacap and growth stocks gained, with Nvidia adding 1.6% and Meta Platforms up 1.4%, buoying the S&P 500 and the tech-heavy Nasdaq.

Apple's market capitalization stood at $3.84 trillion as the world's most valuable company inched closer to the $4 trillion milestone.

Trading volumes are expected to thin, with U.S. stock markets closing early on Tuesday and shutting for Christmas on Wednesday.

"It's a Monday with very few catalysts to drive (broad market) sentiment, and we're going to have low volume, likely volatile trading as we work our way out of this year," said Art Hogan, chief market strategist, B Riley Wealth.

After a solid run since the November presidential election, Wall Street's rally hit a bump this month, especially after the U.S. Federal Reserve forecast just two 25-basis-point rate reductions for 2025 - down from its September view of four cuts - and raised its annual inflation outlook.

Money markets expect roughly two 25-bps reductions in 2025, which would bring the benchmark rate to a range of 3.75% to 4.0%, from about a 3.50 to 3.75% range two weeks ago.

"We would rather have the Fed cut fewer times in a strong economy, than have to cut more times in a weakening economy," Hogan said.

Markets are also entering a historically strong period for U.S. stocks. Since 1969, the last five trading days of the year, combined with the first two of the following year, have yielded an average S&P 500 gain of 1.3% - a period known as the "Santa Claus Rally", according to the Stock Trader's Almanac.

Qualcomm's shares rose 2.8% after a jury found its central processors are properly licensed under an agreement with UK-based Arm Holdings. Shares of Arm, which has vowed to seek a fresh trial, fell about 5%.

Shares of Rumble jumped 41.5% after the video-sharing platform said it has received a strategic investment of $775 million from cryptocurrency firm Tether.

Eli Lilly gained 1.6% after the U.S. Food and Drug Administration approved the drugmaker's weight-loss treatment, Zepbound, for obstructive sleep apnea. Shares of sleep apnea device makers ResMed and Inspire Medical fell 4.1% and 3.1%, respectively.

Declining issues outnumbered advancers by a 1.77-to-1 ratio on the NYSE, and by a 1.3-to-1 ratio on the Nasdaq.

The S&P 500 posted two new 52-week highs and one new low, while the Nasdaq Composite recorded 26 new highs and 43 new lows.