* Osram issues second profit warning in two months
* Blames switch to WLTP standards, trade spat with U.S.
* Says will review medium-term targets
* Shares drop 22 percent to 3.5-year low (Adds CFO, CEO comments, share price, details)
FRANKFURT, June 28 (Reuters) - Automakers are holding off buying LED lights amid uncertainty over a looming trade war between the United States and China and new car testing standards, German lighting group Osram said, slashing its profit guidance a second time in two months.
Shares in Osram dropped 22 percent to 32.85 euros, their lowest level in three and a half years, by 1421 GMT. The group is due to publish full fiscal third-quarter results on Aug. 1.
"We see that clients are pushing orders into future months," finance chief Ingo Bank told analysts during a conference call.
He said that none of Osram's customers had cancelled their orders so far but declined to speculate on when and at what price they would end up taking deliveries.
Trump last week threatened to impose a 20 percent tariff on all imports of EU-assembled cars on the grounds that trade imbalances on many products threaten U.S. national security.
He is separately threatening to impose tariffs on up to $200 billion of Chinese goods. China has warned it will retaliate with levies on U.S. products.
Germany's Daimler, the maker of Mercedes-Benz cars, last week cut its 2018 profit forecast, and BMW said it was looking at "strategic options" because of the trade war between China and the United States, sparking fears of a wave of earnings downgrades in the auto industry.
In addition, carmakers are grappling with a switch to a new Worldwide Harmonised Light Vehicle Test Procedure (WLTP), which is causing delays to official road certification and sales.
Volkswagen said this week it would shut its main Wolfsburg factory for 1-2 days a week between August and the end of September to deal with problems caused by the new tests.
Osram, which generates around 50 percent of its sales and a large part of its earnings with customers in the automotive industry, said it still believed in the autos sector's long-term potential but would nonetheless review its medium-term targets by this autumn.
"It is too early to say what will happen in 2019. But this WLTP effect is temporary. It's a timing issue, not a structural issue," Chief Executive Olaf Berlien said.
"I am optimistic that the normal growth will come back," he added.
In addition to uncertainty in the automotive sector, Osram has been hit with two customers pushing back projects into its next fiscal year, it said on Thursday.
The group now expects its revenues to grow by 1 to 3 percent in the fiscal year through end-September, with adjusted earnings before interest, taxes, depreciation and amortisation (EBITDA) at 570 million to 600 million euros ($659-694 million).
When it cut its guidance in late April it forecast revenue growth of 3 to 5 percent and adjusted EBITDA of 640 million euros.
$1 = 0.8644 euros Reporting by Maria Sheahan; Editing by Christoph Steitz and Alexandra Hudson