NEW DELHI (AP) — U.S. President Donald Trump has vowed additional 25% tariff on India for its purchases of Russian oil, bringing the combined tariffs imposed by the United States on its ally to 50%. India has called the additional tariffs “unfortunate.”

Indian exports to the U.S. now face a hefty 50% tariff, jolting longstanding efforts by both Washington and New Delhi to deepen ties.

U.S.-India ties are facing their most serious crisis in years after talks with India failed to produce a trade agreement.