The "window is still open" for the U.S. and North Korea to strike a deal, Washington's top envoy to the country told lawmakers Wednesday, stressing that his pending promotion to Deputy Secretary of State will send a message to Pyongyang that the Trump administration is elevating the issue to the highest levels of government.

Stephen Biegun made the comments during an appearance before the Senate Foreign Relations Committee — a required step in the U.S. Senate's confirmation process for a high-ranking federal official, and a rare opportunity for members of Congress to directly and publicly interrogate President Donald Trump's top envoy in negotiations with Pyongyang.