Crude climbed to a nine-month high on Friday, as supply disruption fears took center stage.
Stocks fluctuated on Tuesday a day before the Federal Reserve's policy decision.
Treasury prices fell after consumer prices recorded their largest increase in more than a year, which may prompt the Fed to adopt a hawkish tone.
European shares closed higher on Tuesday, bouncing back from Monday's losses.
Gold settled lower, backing away from the previous session's three-week highs as a stronger dollar quelled appetite for safe-haven assets.
Gold was below a three-week high on Tuesday as Iraq tensions attracted some safe-haven bids, while investors waited for a Fed meeting this week.
Brent held steady above $113 per barrel while U.S. crude weakened slightly, as speculation about Iran and the West offset fears about Iraq.
U.S. stock index futures pointed to a flat-to-lower open on Wednesday, as investors awaited this month's policy decision from the Fed.
U.S. stock index futures were higher on Tuesday, as European markets shook off fears over developments in Iraq, Ukraine and Argentina.
Most U.S. Treasury prices were flat after solid economic data overcame earlier strength, as fighting overseas boosted demand for safe-haven bonds.
European shares closed lower on Monday amid concerns of escalating tensions in Iraq and rising oil prices.
The dollar was up around a third of a percent against the yen as markets listened to the Bank of Japan's latest comments on policy on Friday.
Crude pushed higher in choppy trading as advances by Sunni insurgents in Iraq fueled concerns over a potential disruption to oil exports.
The Australian dollar fell more than half a percent against the U.S. dollar on Tuesday after the RBA expressed economic recovery doubts.
Asian equities finished a choppy session mixed on Monday with escalating violence in Iraq weighing on sentiment.
Stocks rose on Friday, with equities on track for weekly losses.
U.S. stock index futures traded lower on Monday, with risk aversion growing due to concerns about Iraq, and to a lesser extent, Ukraine.
European shares closed slightly down flat on Friday amid concerns of escalating tensions in Iraq and rising oil prices.
Sectarian violence in Iraq sent oil skyrocketing, propelling Brent and West Texas Intermediate up two percent.
Palladium tumbled to a one-month low as investors awaited confirmation that South Africa's longest mining strike would end soon.
Get the best of CNBC in your inbox
Currency wars are one reason Michael Farr thinks the Fed will either defer the first rate hike to next year or do one small move and then pause.
The U.S. economy is being pulled in opposite directions by two factors, Pimco's Joachim Fels said.
A stimulus from the Chinese government, even if effective, may not buffer big tech companies like Apple and Cisco from a slowdown in China sales.