UPDATE 1-Saudi energy minister says Aramco IPO could still happen in 2018

(Adds detail, background on IPO)

WASHINGTON, March 22 (Reuters) - Saudi Arabia may still move forward with an initial public offering (IPO) for state oil company Saudi Aramco on an international exchange such as London or New York in the second half of 2018, despite previously raising doubts it could be delayed to next year, Saudi Energy Minister Khalid al-Falih said on Thursday.

Falih told Reuters in an interview in Washington the oil giant could be floated either domestically or internationally late this year. New York is still in the running for the IPO but Saudi officials still need to weigh the risk of potential "frivolous lawsuits" in its final decision.

"We have prepared all documentation to be ready to do both domestic and international listings," Falih said. "We have not closed the door on 2018." Saudi Arabia is planning to list up to 5 percent of Saudi Aramco in an initial public offering that could value it at up to $2 trillion and make it the worlds biggest oil company by market capitalization.

Falih said officials have prepared documentation to be ready to do both a domestic and an international listing.

Despite comments he made earlier this month that Aramco was too important to risk listing in the United States because of litigation concerns, such as existing lawsuits against rival oil companies for their role in climate change, he said New York is still in the running for the IPO.

"We have concerns obviously Aramco is too big and too valuable and too important and we could be potentially at risk from some frivolous lawsuits and litigation that we have to consider in our final decision," he said.

Legal challenges could arise from a U.S. law that would allow U.S. victims of militant attacks to sue foreign governments for compensation. (Reporting by Timothy Gardner and Valerie Volcovici Editing by James Dalgleish)