(Reuters) -U.S. stock index futures steadied on Thursday after a fall in the previous session, when Treasury yields surged, as investors worried President Donald Trump's tax and spending bill could sharply inflate the country's debt burden.

If passed, the legislation that Trump nicknamed "one big beautiful bill" will add $3.8 trillion to the $36.2 trillion U.S. debt pile over the next decade, according to the nonpartisan Congressional Budget Office.

The House of Representatives voted roughly along party lines on Thursday during a debate that will lead to a vote on passage later in the morning.

"The growing mountain of U.S. debt is causing ripples of worry across financial markets, with signs investors are baulking at financing the Trump administration," said Susannah Streeter, head of money and markets at Hargreaves Lansdown.

At 05:13 a.m. ET, Dow E-minis were down 49 points, or 0.12%, S&P 500 E-minis were up 4.5 points, or 0.08%, and Nasdaq 100 E-minis were up 37.5 points, or 0.18%.

All three main stock indexes saw their biggest single-day percentage drops in a month on Wednesday, as Treasury yields spiked on worries about mounting U.S. debt.

Longer-dated Treasury yields eased a touch, coming off their multi-month highs on Thursday. Those on the 10-year benchmark fell 2 basis points to 4.57%.

Most megacap and growth stocks inched higher in premarket trading, with Google-parent Alphabet leading with a 1.3% rise.

Cryptocurrency and blockchain-related stocks jumped as bitcoin, the world's biggest cryptocurrency, climbed to a record high.

Exchange operator Coinbase advanced 2.5%, bitcoin stockpiler Strategy gained 1.4% and crypto miners including MARA Holdings added 4%.

Snowflake jumped 10.2% after the cloud computing firm raised its fiscal 2026 product revenue forecast.

U.S. stocks have had a solid month so far, with the S&P 500 climbing more than 15% from its April lows, when Trump's reciprocal tariffs rattled global markets.

A pause in tariffs, a temporary U.S.-China trade truce and tame inflation data have pushed equities higher, although the S&P 500 is still about 3% off its record highs.

At least two Federal Reserve officials including New York Fed President John Williams are slated to speak later in the day.

Weekly jobless claims data and preliminary numbers of the May Purchasing Managers' Index are also scheduled to be released.

Among stocks, shares of solar energy companies including First Solar dropped 3.4% as Trump's tax-cut bill is expected to end a number of green-energy subsidies.

Insurer UnitedHealth extended losses after a nearly 6% drop in the last session and was down 1.8%.

Earnings season is winding down, with more than 90% of S&P 500 companies having reported numbers. Analog Devices is due to report results before the bell and Nvidia is slated to report next week.