LONDON (Reuters) - More than a third of emerging market companies are likely to be "meaningfully" impacted by U.S. trade tariffs when they hit, analysts at investment bank JPMorgan have estimated.

Including the likelihood that Chinese and Mexican firms are hit hard, they estimated that 36% of the more than 750 companies in the bank's closely followed CEMBI EM corporate debt index would fall into that bracket. Some 16% of firms - and included in that bracket - could see a "significant" impact.

They described the 36% figure as "not negligible", although they also pointed out that more than half of the firms in the index might only be "minimally" hit.

Companies from China and Mexico make up 6.3% and 4.3% of the CEMBI index respectively, while a sector breakdown of the most significantly impacted firms showed 9% are industrial firms and 6.5% in metals and mining.

JPMorgan's report also estimated that the average interest rate premium, or spread, that investors demand to hold EM corporate debt doesn't currently suggest markets are pricing in the kind of harsh tariffs that would cause a U.S. recession.

That spread has risen to 226 basis points from 190 basis points in recent weeks, although that is still more than 100 basis points below its post-2010 average of 320 basis points.

If recession worries do start to build, though, the spread could widen to closer to 300 basis points, similar to the pattern seen in 2018 when U.S. President Donald Trump first sparked trade tensions.

Back then, the CEMBI spread widened 132 basis points, or 60%, in roughly nine months, which was more than both EM hard currency sovereign debt spreads and U.S. corporate credit spreads.

This time around, Asia shows a relatively smaller weight of exposed sectors at 21%, as the slightly higher weight of industrials is more than offset by a much lower contribution from the commodities sectors.

The region's firms make up just over 40% of CEMBI and it has a hefty group of tech exporters that may be affected by tariffs on semiconductors.

In Latin America, Mexican companies appear the most vulnerable, unsurprisingly given that nearly 80% of Mexico's exports are directed to the U.S., whereas other major economies like Brazil should be less exposed.

"There will naturally be differentiation within the countries in terms of sectors that are affected more or less, and those that have further mitigating factors such as U.S. operations," JPMorgan's report, published on Wednesday, said.