* Concerns about possible North Korean test also underpin yen
* Euro edges back toward 6-month highs touched after Macron's win
TOKYO, May 10 (Reuters) - The dollar slid on Wednesday and the perceived safe-haven yen gained after U.S. President Donald Trump abruptly fired FBI Director James Comey in a move that shocked Washington.
Comey had been leading his agency's investigation into alleged Russian meddling in the 2016 U.S. presidential campaign and possible collusion with Trump's campaign. Democrats immediately accused Trump of acting out of political motives.
Any U.S. political turmoil tends to weigh on the dollar, as a divided Congress could derail Trump's promised tax reform and stimulus steps.
The dollar index, which tracks the greenback against a basket of six major currencies, slipped 0.2 percent to 99.437 , moving away from a three-week high of 99.688.
The dollar dipped 0.2 percent against its Japanese counterpart to 113.77 yen, below its overnight high of 114.325, which was its highest since March 15.
Rekindled fears that North Korea could be gearing up for another weapons test also underpinned the yen.
"In the early morning hours of Asian trade, the yen started to strengthen, and it could have been the reaction of overseas markets to a North Korean diplomat's comments," said Mitsuo Imaizumi, Tokyo-based chief foreign-exchange strategist for Daiwa Securities.
In an interview with Sky News on Tuesday, Pyongyang's ambassador to the UK, Choe Il, said North Korea is ready to conduct a sixth nuclear test. Observers of that country have said such a test was likely, but his comments reminded markets that tensions could escalate on the recently calm Korean peninsula.
South Korea's newly elected liberal leader Moon Jae-in, who will be sworn in on Wednesday, is expected to try to engage Pyongyang with dialogue and aid, breaking from his predecessor's hardline policies.
"With this in the background, as well as the present uncertainty in the U.S., the dollar will trade heavily today below the 114-yen level," Imaizumi said.
Lower U.S. yields also pressured the dollar. The benchmark 10-year U.S. Treasury yield slipped to 2.397 percent in early Asian trade, down from Tuesday's U.S. close of 2.407 percent.
It scaled five-week peaks overnight, as interest rate futures priced in close to a 90 percent chance that the U.S. Federal Reserve will raise interest rates again at its next meeting in June.
The euro added 0.1 percent to $1.0885, edging back toward six-month highs hit after centrist Emmanuel Macron's victory in the French presidential election on Sunday.
European Central Bank chief Mario Draghi is scheduled to speak at the Dutch House of Representatives later on Wednesday. Investors will be waiting to see if he alters his dovish tone in light of recent strength in the euro zone economy.
Reporting by Tokyo markets team; Editing by Richard Pullin