The US dollar fell against the Japanese yen on Thursday as investors pushed into safe-haven assets on reports the United States and China were struggling to finalize a "phase one" trade deal and as the domestic impeachment inquiry into US President Donald Trump intensified.

The Japanese yen was up 0.39% to 108.4 against the dollar, having risen to a 10-day high earlier in the session. The Swiss franc also benefited, up 0.16%, with the dollar index down 0.22% to 98.159. That risk-off move also bolstered US Treasury bond prices and hit the Dow Jones and Nasdaq indexes, which also contributed to the dollar's fall.

"We started off earlier today with some mild risk aversion. That has continued - over the course of the session - to push dollar/yen down," said Shaun Osborne, chief foreign exchange strategist at Scotia Capital.

The Financial Times on Thursday afternoon reported that China and the United States were struggling to reach a "phase one" deal and may not settle ahead of Dec. 15, when US tariffs on Chinese goods are set to go into effect. Washington, according to Financial Times sources, does not yet believe Beijing has made sufficient concessions on matters including intellectual property and agricultural purchases to warrant a roll-back.

"There seems to be this eternal cheerleading for a trade deal from the White House that may be having less impact on the markets," said Osborne.

"The reality is we're still waiting for this phase one deal, we have been waiting for some time and it doesn't look like it's anywhere close to being done. And I rather suspect that given everything else that is going on, China might be just be deciding it can afford to wait here and see what happens politically in the US"

House of Representatives Speaker Nancy Pelosi said on Thursday that Trump already has admitted to bribery in the Ukraine scandal at the heart of a Democratic-led inquiry, accusing him of an impeachable offense under the US Constitution.

Also on Thursday, the Labor Department reported that US producer prices increased by the most in six months in October, further bolstering the Federal Reserve's stance that it will probably not cut interest rates again in the near term.

"The fact that wholesale inflation did surprise to the upside I think does speak to the narrative that core PCE... should hit or even breach the Fed's target of 2%," said Paresh Upadhyaya, director of currency strategy and portfolio manager at Amundi Pioneer Investments.