The once puny dollar is starting to look mightier again. And that could be bad news for Corporate America.

The US Dollar Index, which measures the value of the greenback against the euro, the yen and several other major global currencies, has been on a tear. It's risen more than 3.5% in just the past two weeks and is now up slightly for the year.

It wasn't that long ago that the dollar was languishing, and big companies such as Nike (NKE), Costco (COST), Oracle (ORCL) and FedEx (FDX) were crediting the weaker dollar for boosting their earnings.

A weaker dollar lifts the profits of multinational companies because it makes their products less expensive in foreign markets. There's an accounting benefit, too: Companies get to report higher revenue from abroad when they translate their international sales back into dollars.

So the dollar's rally is suddenly turning into a problem.

The chief financial officer of the cruise company Royal Caribbean (RCL), which is headquartered in Miami, said last week that the greenback's rebound ate into profit for its most recent quarter.

The CFO of Iron Mountain (IRM), a Boston data storage company, noted in its earnings call that it had benefited from "favorable currency translation" in the first quarter — but warned that exchange rates may not provide a similar lift for the remainder of the year.

Apple (AAPL) even acknowledged in its earnings call Tuesday that a stronger dollar could hurt profit.

"Because about two-thirds of our company is outside the United States, a weak dollar is a positive for our gross margins," said Apple chief financial officer Luca Maestri. "A strong dollar, as it's been during the last four years, has been a bit of a headwind."

Many analysts think this will continue because the Federal Reserve is expected to raise interest rates at least two more times this year, and perhaps three more times in 2019. That could boost the dollar further, especially because the European Central Bank isn't likely to hike rates anytime soon.

Related: The Fed is likely to hike rates faster than once thought

Lukman Otunuga, research analyst at currency brokerage firm FXTM, wrote in a report Wednesday that an improving US economy should lead to "rising inflation expectations supporting the prospect of higher interest rates" from the Fed.

So Otunuga thinks the dollar could keep hitting new highs for the year as long as the economy keeps gaining momentum.

All eyes will turn next to Friday's jobs report. A better than expected number of jobs added could lead to even more optimism about the economy, which should lift the dollar further.

Boris Schlossberg, managing director of currency strategy for BK Asset Management, said in a report early Wednesday that "a solid 200K print from ADP" could boost the dollar.

Schlossberg was referring to the widely watched private sector jobs number, which the payroll processing and HR company ADP (ADP) puts out days before the official government report. ADP said Wednesday that 204,000 jobs were added — and the dollar immediately rallied on the news.

So if the official jobs number on Friday is similarly strong, the dollar could keep rallying. And it will be interesting to see how the Trump administration reacts.

President Trump once touted the benefits of the weak dollar, but he has changed his tune in recent months.

After Treasury Secretary Steven Mnuchin described a weaker dollar as "good for trade," Trump told told CNBC in January that the dollar will get "stronger and stronger."

It looks like he was right. The dollar is enjoying a resurgence. The question is whether that will do more harm than good for giant US companies, the stock market and the broader economy.