Oil futures climbed on Wednesday even as data showed inventories of U.S. crude increased.
U.S. futures trimmed gains on mostly weak U.S. data but still signaled a mildly higher open as investors welcomed comments from Yellen's speech.
Gold rose, recovering from the previous day's seven-week lows, after comments from Janet Yellen suggested no rush to raising interest rates.
Asian equities turned mixed amid choppy trade on Wednesday after China's manufacturing sector surprised markets with growth for the first time in three months.
U.S. stocks closed at highs as Yellen's congressional testimony indicated that a rate hike would likely come later rather than sooner.
European equities ended higher after Greece's bailout extension plan was approved, as U.S. Fed Chair Janet Yellen said rates would not anytime soon.
The dollar edged down against the yen Janet Yellen suggested the Fed won't be rushed into kicking off the U.S. interest rate tightening cycle.
Gold extending earlier losses after Fed Chair Janet Yellen said there was no need to hike interest rates over the next few months.
U.S. stock index futures signaled a flat open on Wednesday after comments from Fed Chair Yellen's speech to Congress.
Asian indices mostly advanced on Tuesday to hit new highs, but trading remained cautious ahead of Federal Reserve Chair Janet Yellen's testimony.
U.S. stocks pulled back from Friday's records to close narrowly mixed ahead of Fed Chair Janet Yellen's remarks over the next two days.
U.S. government debt prices were little changed on Monday ahead of Federal Reserve Chair Janet Yellen's address to Congress this week.
European equities finished higher on Monday with investors cheering a deal to extend Greece's bailout program by four months.
Gold fell to its lowest in seven weeks, as the dollar and shares gained after a Greek debt deal was struck, removing investor flight for safety.
Nigeria's oil minister indicated OPEC would hold an emergency meeting to discuss the oil price slide, the Financial Times reported.
The Swiss franc shed over 1 percent against the dollar, dropping towards five-week lows as some of the Greece-related safety flows waned.
U.S. stock index futures signaled a flat open on Tuesday, as investors await hints on the timing of a rate rise at Fed Chair Janet Yellen's speech.
Asian markets mostly rose on the first trading day of the Year of the Sheep, buoyed by a bailout deal between Greece and the euro zone last week.
U.S. stocks rallied on Friday to close at highs on an eleventh-hour resolution between Greece and its creditors in the euro zone.
U.S. government debt prices fluctuated on Friday, after data showed new claims for unemployment benefits fell more than expected.