Senate Republicans are negotiating among themselves over how to respond to President Trump's trade agenda as they brace for new tariffs on the European Union and a trade deal with China that some fear could leave American farmers worse off.

There are divisions over whether to send a stern message to the White House with a tough bill that's likely to get vetoed - or a more modest proposal that could actually get Trump's signature and become law.

It was a dilemma that GOP leaders eschewed altogether in the run-up to the 2018 midterm elections, deciding not to advance legislation curbing Trump's power to impose tariffs for fear an intraparty fight could hurt voter turnout.

This year, however, there is strong support from influential members of the Senate GOP for reining in Trump's tariff power but disagreement over exactly how to proceed, putting Majority Leader Mitch McConnell (R-Ky.) in a bind.

Senate Finance Committee Chairman Chuck Grassley (R-Iowa) says he will introduce legislation in the coming weeks that would strengthen what his office calls "checks and balances between Congress and the executive branch by imposing new consultation and reporting requirements."

He says that any trade restrictions imposed by the president would be limited to a defined period of time unless extended by an act of Congress.

But Republicans on the Finance panel are divided over how hard to push back against Trump, with two leading members - Sens. Rob Portman (R-Ohio) and Pat Toomey (R-Pa.) - advocating for different, competing approaches that Grassley is trying to meld together behind the scenes.

Grassley, Portman and Toomey met with Trump last month to express their concerns about the impact of tariffs on the global economy.

Time is of the essence as Trump threatened last week to impose $11 billion in tariffs on European Union products in retaliation for EU subsidies to Airbus, putting new pressure on GOP lawmakers to act.

The White House threatened earlier this year to impose a 25 percent tariff on imported cars, which could boomerang on several Republican states if trade partners impose retaliatory penalties.

GOP lawmakers fear that could hit states such as Ohio, Indiana, Texas, Tennessee, Missouri, Kentucky, Alabama and Mississippi, which all rank in the nation's top 10 for auto manufacturing.

McConnell, who is up for reelection in 2020, doesn't seem eager to confront the president head on. He has made it his reelection strategy to stick as close to Trump as possible and won't say whether he'll bring legislation curbing his tariff authority to the floor.

Asked if the legislation is needed, McConnell told reporters, "I don't have anything to say about that, I haven't looked at it."

In addition to senators concerned about auto manufacturing, farm-state Republican lawmakers worry that Trump's anticipated trade deal with China will hurt U.S agricultural interests.

Some farmers fear that Trump will negotiate an agreement under which China would buy a certain amount of soybeans and pork but leave other U.S.-produced commodities in limbo.

Mark Powers, the president of the Northwest Horticultural Council, which represents fruit growers in the Northwest, told Bloomberg News that his members are staring down another year of tariffs.

"We're disappointed. Clearly the priority lies elsewhere," he said of the expectation that Trump's trade deal will alleviate pressure on some but not all U.S. agricultural commodities.

Economists say the lingering trade war is dampening global growth, with the International Monetary Fund warning last week that economies around the world are slowing faster than expected.

Though the biggest obstacle to quick action in the Senate is disagreement among Republicans over how hard to push back on Trump's trade policies, they are also unsure of how much Democratic support to expect.

While Democrats can be counted on to oppose most anything that Trump wants to do, his trade policies have put them in a quandary as Democratic constituent groups such as labor unions are critics of globalization and free trade.

Portman has opted to work closely with the administration on legislation that could have a chance to win the president's signature and become law. He has consulted with U.S. Trade Representative Robert Lighthizer, senior economic adviser Larry Kudlow, Kudlow's predecessor Gary Cohn and senior trade advisor Peter Navarro.

Portman has legislation that would require the Department of Defense, instead of the Department of Commerce, to justify the national security concerns invoked to impose new tariffs under Section 232 of the 1962 Trade Expansion Act. It would empower Congress to block them by passing a resolution of disapproval, expanding the check provided in the original trade law, which only applied to action on oil imports.

Portman's legislation, however, would only apply prospectively and not reach back in time to undo some of Trump's controversial trade actions, which makes it more palatable to the White House.

His bill is also sponsored by Sens. Lamar Alexander (R-Tenn.), Deb Fischer (R-Neb.), Todd Young (R-Ind.), Joni Ernst (R-Iowa), Doug Jones (D-Ala.), Dianne Feinstein (D-Calif.) and Kyrsten Sinema (D-Ariz.).

Senate Republican critics of Portman's plan, however, say it doesn't have sharp-enough teeth and argue there's no mechanism to guarantee the disapproval resolution floor time.

Toomey's bill is tougher. It would give Congress 60 days to approve any proposed tariffs under Section 232. If Congress fails to pass an approval resolution within that period, the president's proposed tariffs would have no effect. Motions to proceed to those approval resolutions would be privileged in both chambers and could not be filibustered. They would be automatically discharged out of committee after 10 days.

Toomey's legislation would also transfer more authority to the Department of Defense to determine whether a foreign trade practice poses a national security threat to the United States.

Unlike Portman's bill, however, the Toomey proposal would apply retroactively. Any Section 232 tariffs and quotas imposed over the past four years would be repealed unless Congress passes approval resolutions within 75 days of enactment.

Its co-sponsors are Sen. Ben Sasse (R-Neb.), Mark Warner (D-Va.) and Maggie Hassan (D-N.H.).

A senior GOP aide noted that several provisions in the Portman and Toomey proposals are irreconcilable, such as the conflicting oversight pathways - either a disapproval or an approval resolution - and the issue of retroactivity.

"These are either/or propositions, you can't have some of them both ways," the aide said.

Critics of Toomey's legislation say that it's destined for a presidential veto, as Trump won't be willing to give up his tariff powers. They say Portman's plan has a better chance of becoming law because of his close consultation with White House advisers.

The sponsors of the competing bills say they expect Grassley to have a hearing on the legislation after the two-week April recess.