NEW YORK ( TheDeal) -- The proposed $13.6 billion acquisition of Life Technologies Corp. ( LIFE) by Thermo Fisher Scientific Inc. ( TMO) faces few substantive regulatory hurdles though the companies warn that they may not obtain regulatory approval until January 2014. Analysts says that's because of uncertainty about the timing of overseas antitrust approvals, particularly from China. The companies announced their plans to merge on April 14 with Thermo Fisher agreeing to pay $76 per share in cash. According to the companies' agreement, if failure to obtain necessary antitrust approval prevents the merger from closing by Jan. 14, 2014, the per share price will increase by 0.6 cents each day afterward. Life Technologies was little changed at $73.52, having gained 8.2% since April 12. Thermo Fisher was falling 0.5% to $83.51, a 4.8% since a day before the deal was made public. Since the, Thermo Fisher CEO Marc Casper has declined to get into specifics about the antitrust review, saying only that the company has good lawyers. "It's obviously an area that we're very well advised," he said shortly after the deal was announced. "We have terrific counsel in this area. And as we look at the process going forward, we would expect to close the transaction early in 2014. And certainly we're not going to speculate on what the governments might think, but we feel good about the process going forward." During an April 15 conference call, JPMorgan Chase & Co. analyst Tycho Peterson suggested that there might be overlaps in bio-production services and polymerase chain reaction products used to copy DNA, but Casper wouldn't comment on the suggestion. Another analyst who has examined the deal said both companies' extensive product lines make it difficult to predict exactly how much competitive overlap there is and which products, if any, might be required to be divested. The Federal Trade Commission will review the deal in the U.S. The biggest uncertainly, the analyst said, is predicting the timing of approvals overseas, particularly from China's Ministry of Commerce, which is prone to lengthy antitrust reviews even when it ultimately imposes no conditions on a merger approval.