The United States has warned Turkey that its planned purchase of the Russian S-400 air defence system would put at risk Ankara’s participation in the F-35 jet program and could lead to Washington imposing sanctions on Ankara, US Department of State spokesperson Robert Palladino said in a press briefing.

"We've clearly warned Turkey that its potential acquisition of the S-400 will result in a reassessment of Turkey's participation in the F-35 program and risk other potential future arms transfers to Turkey, as well as lead to potential sanctions under the Countering America's Adversaries Through Sanctions Act," Palladino said on Tuesday.