U.S. stocks ended higher on Monday amid market speculation on the timing of the tax reform.

The Dow Jones Industrial Average increased 17.49 points, or 0.07 percent, to 23,439.70. The S&P 500 rose 2.54 points, or 0.10 percent, to 2,584.84. The Nasdaq Composite Index was up 6.66 points, or 0.10 percent, to 6,757.60.

The market had rallied to record highs amid renewed expectations that the U.S. Congress, along with the Trump administration, would be able to move forward with tax reform in 2017.

However, rising concerns emerged after the Senate Republicans on Thursday unveiled a plan to overhaul the U.S. tax code that contains key differences from a comparable House tax plan.

The Senate bill would delay a corporate tax rate cut from 35 percent to 20 percent until 2019, denting investors' hope for a new tax plan before the end of this year.

Republicans in the U.S. House of Representatives announced earlier this month the long-awaited bill to overhaul the U.S. tax code in decades by significantly cutting individual and corporate income taxes.

It would reduce the number of personal income tax brackets from seven to four, while keeping the top individual income tax rate at 39.6 percent. It would also cut the corporate income tax rate to 20 percent from 35 percent.

In corporate news, China's ecommerce company JD.com reported quarterly revenue of 12.58 billion U.S. dollars, higher than market consensus and up 39 percent from last year.

The online retailer also reported adjusted earnings of 23 cents, beating market expectations. Shares of JD jumped 3.45 percent on Monday.