Judy Woodruff:

Mr. Trump said he would announce which countries would be targeted next week. There would be 25 percent tariffs on steel and 10 percent on aluminum.

A number of Republican allies, including the speaker of the House, Paul Ryan, took issue with the president's decision.

The president has repeatedly threatened to take tougher measures against China.

And the Wall Street Journal's Greg Ip is here now to explain what all of this might mean.

Greg, thank you for being with us.

Before we get into the reaction to all this, including in the markets, what would tariffs at this level, 25 percent on steel, 10 percent on aluminum, generally, what would that mean?