Thousands of Iranians hold banners and posters as they take part in a pro-government rally in Mashhad, Iran on January 4, 2018.

Oil prices edged higher to settle in the green on Monday, after a volatile session that saw prices spike 2% in early trading, before dipping into negative territory, and then finally settling little changed. The price action came despite ongoing fears that Iran will retaliate against U.S. interests.

U.S. West Texas Intermediate gained 22 cents, or 0.3%, to settle at $63.27 per barrel. Earlier, WTI rose to $64.72, its highest level since April. International benchmark Brent crude gained 31 cents to settle at $68.91 per barrel, after briefly dipping into negative territory. Earlier in the session it hit a more than three-month high of $70.74.

"The calculus over whether or what Iran will do is a dicey one," Again Capital's John Kilduff said to CNBC Monday. "With Iran sitting on its hands, for now, some of the anxiety is coming out of the price. The complacency may be misplaced, however ... There is a significant deployment of U.S troops to the region underway," he added.

Following Thursday's death of top Iranian commander Qasem Soleimani, Iran vowed to retaliate, which Wall Street analysts said would determine the direction of oil's next move.

For instance, if the nation targets production in Saudi Arabia or Iraq — OPEC's two largest producers — prices could move higher.

Not that long ago a geopolitical event of this nature would have likely triggered a larger spike in oil prices, which is indication that oil has become a "lagging indicator," RBC head of commodity research Helima Croft said Monday.

She added that there are likely "a lot of market participants who are waiting to see if there is an actual physical supply disruption," that there is a "segment of the market that probably believes that this will blow over."

On Sunday an Iranian state-run television broadcast said that the nation would no longer respect uranium enrichment restrictions set forth in 2015's nuclear deal, in an escalation of tensions.

On Friday Brent gained 3.55%, with WTI gaining 3.06%, and both posted their fifth straight week of gains.