A selloff in crude oil proved another roadblock in the Dow Jones Industrial Average's pursuit of 20,000 on Monday. 

The Dow slid 0.34% to 19,895 on Monday, though remained one rally away from clinching its next milestone. The S&P 500 was down 0.32%.

The Nasdaq was the only index in the green on Monday, rising 0.15% and reaching another intraday record of 5,541. Deals-related rallies in health care helped to boost the index.

Merrimack Pharmaceuticals (MACK) - Get Merrimack Pharmaceuticals, Inc. Report was 4% higher after drugmaker Ipsen agreed to buy some of its assets, including its drug for pancreatic cancer, in a deal worth more than $1 billion. Merrimack also said it would eliminate about 80% of its staff as it refocuses its pipeline.

Ariad Pharmaceuticals (ARIA) surged 73% after Takeda Pharmaceutical agreed to acquire the drugmaker in a deal worth $5.2 billion. Takeda offered to purchase Ariad for $24 a share, valuing the drugmaker at a premium of 75% compared to its closing price on Friday of $13.74. The all-cash deal is expected to close by the end of February.

Other drugmakers including Gilead Sciences (GILD) - Get Gilead Sciences, Inc. (GILD) Report , Celgene (CELG) - Get Celgene Corporation Report , Amgen (AMGN) - Get Amgen Inc. Report  and Novartis (NVS) - Get Novartis AG Sponsored ADR Report moved higher, while the Health Care SPDR ETF (XLV) - Get Health Care Select Sector SPDR Fund Report slid 1.6%. 

Dow 20,000 came agonizingly close on Friday, but building momentum flagged in the final moments to fall short of the milestone. The Dow came within a point of the level in the afternoon session before backing off, just as it has for weeks. The S&P 500 and Nasdaq each closed at fresh records on Friday.

Crude oil prices fell below $53 a barrel on Monday, continuing to trade off of data late Friday that showed rising U.S. production. A weekly reading on U.S. activity showed the number of U.S. oil rigs climb for the 10th consecutive week in a row.

Commodities trading has been erratic in the past week as investors weigh U.S. production against an agreement among major oil-producing nations designed to rebalance markets. A production cut agreement among Organization of Petroleum Exporting Countries and other non-OPEC producers took effect at the beginning of the year.

"With the market having already attracted a large volume of buying in anticipation of a rebalance market and months of price gains on the announcement of talks, the progress of talks, and the announcements of the production cut agreements, the market runs the risk of a "sell the news" reaction even if compliance is relatively good," said Tim Evans, energy futures specialist at Citi, in a note. 

West Texas Intermediate crude closed 3.8% lower at $51.96 a barrel on Monday.

The energy sector was the worst performer on Monday. Major oilers including Exxon Mobil (XOM) - Get Exxon Mobil Corporation Report , Chevron (CVX) - Get Chevron Corporation Report , Halliburton (HAL) - Get Halliburton Company (HAL) Report and Marathon Petroleum (MPC) - Get Marathon Petroleum Corporation (MPC) Report slid, while the Energy Select Sector SPDR ETF (XLE) - Get Energy Select Sector SPDR Fund Report fell 1.3%.

Wall Street was also adopting a wait-and-see approach ahead of fourth-quarter earnings later this week. The big banks, as usual, will be among the first to report earnings. Bank of America (BAC) - Get Bank of America Corp Report , JPMorgan (JPM) - Get JPMorgan Chase & Co. (JPM) Report and Wells Fargo (WFC) - Get Wells Fargo & Company Report will report on Friday.

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Average earnings for the S&P 500 in the fourth quarter are expected to increase 4.4% from the same period a year earlier. Earnings growth would mark the second straight quarter of gains after the third quarter broke an earnings recession that lasted for four consecutive quarters. Earnings grew 4% in the third quarter of 2016.

The U.S. economy warrants "somewhat more regular" interest rate hikes, Boston Federal Reserve President Eric Rosengren said on Monday. In a speech in Hartford, Conn., Rosengren said the "economic circumstances have evolved and now imply the need for a different stance of monetary policy." Rosengren is a voting member of the Federal Open Market Committee this year.

Atlanta Fed President Dennis Lockhart brought a more dovish take on Monday afternoon, arguing that the U.S. economy isn't likely to breach higher than 2% growth. In a speech in Atlanta, Lockhart said the U.S. economy would likely reach 2% next year but no higher. "It's less certain that the economy is positioned for a breakout to markedly higher growth on a sustained basis," Lockhart said. 

The British pound tumbled more than 1% overnight after British Prime Minister Theresa May suggested a full withdrawal from the European Union, conflicting with a former ambassador to the EU who had suggested the approach so far had been "muddled." May told Sky News that the U.K. would no longer be a member of the EU and that she would provide "more details in the coming week as we look ahead to triggering Article 50."

Pet health care company VCA (WOOF) - Get Petco Health & Wellness Co. Report agreed to be acquired by Mars Inc. on Monday in a deal worth $9.1 billion. Snacks and petcare company Mars agreed to purchase VCA for $93 a share, a roughly 31% premium to its close on Friday. The deal is slated to close in the third quarter of this year. VCA shares jumped 28%.

Alibaba (BABA) - Get Alibaba Group Holding Ltd. Sponsored ADR Report shares moved 1.1% higher after its CEO Jack Ma met with President-elect Donald Trump at Trump Tower. Trump and Ma characterized the meeting as successful and said the focus was on jobs and small business. 

Urban Outfitters (URBN) - Get Urban Outfitters, Inc. Report fell 2.3% after reporting same-store sales over the critical holiday shopping season. Total same-store sales climbed 1.5%, which was less than expected. Same-store sales at its Urban Outfitters stores increased 3.6%, while Anthropologie sales declined 1%.

Acuity Brands (AYI) - Get Acuity Brands, Inc. Report declined 14% after soft demand crimped quarterly growth over the three months ended November. The lighting company earned adjusted profit of $2 a share, up from $1.77 a share a year earlier. Analysts had anticipated profit of $2.16 a share. Revenue rose 16% to $851.2 million, though fell short of $894.94 million consensus.

Global Payments (GPN) - Get Global Payments Inc. (GPN) Report added 7% after increasing its fiscal 2017 earnings guidance. The check processing company expects to earn an adjusted $3.70 to $3.90 a share over the full year. The company had previously anticipated adjusted earnings of $3.45 to $3.55 a share.

Francesca's Holdings (FRAN) - Get Francesca's Holdings Corporation Report climbed 9% after upping its fourth-quarter outlook. The retailer anticipates earnings for its January-ending quarter between 35 cents and 37 cents a share. Francesca's had previously targeted 33 cents to 37 cents a share. Its fourth-quarter same-store sales outlook was also revised from an expected 1% decline to expected 1% growth.

Fiat Chrysler (FCAU) - Get Fiat Chrysler Automobiles N.V. Report added 2% after outlining plans to invest $1 billion in plants in Michigan and Ohio, adding 2,000 new jobs to the U.S. The move comes after President-elect Trump took aim at a number of automakers via Twitter in which he criticized any plans to ship jobs out of the U.S. and threatened to impose border taxes.

Texas Instruments (TXN) - Get Texas Instruments Incorporated Report was upgraded to outperform from neutral at Credit Suisse. The firm said earnings estimates are above consensus given higher sales and margin expectations.

Coca-Cola (KO) - Get Coca-Cola Company Report was downgraded to sell from neutral at Goldman Sachs. Analysts pointed to structural changes and increased challenges over currency as reasons for the downgrade. Dr. Pepper Snapple (DPS) was upgraded to neutral given its higher exposure to the U.S. market.

McDonald's (MCD) - Get McDonald's Corporation (MCD) Report slipped after selling a majority stake in its operations in China to Carlyle Group (CG) - Get Carlyle Group L.P. Report and a state-backed investment group for around $2.1 billion. The agreement would see McDonald's part with 80% of its 2,200 stores in China and Hong Kong. The world's largest hamburger chain intends to keep a minority stake in the region.