TOKYO, Feb 7 (Reuters) - Japan is on track to post a record trade deficit in January, preliminary data showed on Friday, in a warning sign that consistently weak export demand could weigh on economic growth. The data also provide further evidence that a weak yen is doing more to push up import costs than it is to boost exports as many Japanese manufacturers have shifted factories overseas. A record trade deficit would also suggest that overseas demand may not be strong enough to offset the negative impact of a scheduled sales tax increase in April. "It may be difficult to expect consumption to continue to lead growth as wages will not rise as fast as prices," said Norio Miyagawa, senior economist at Mizuho Securities Research & Consulting Co. "If external demand doesn't pick up, the overall trend for growth would weaken." For the first 20 days of January, Japan's trade deficit was 2 trillion yen ($19.6 billion), data from the finance ministry showed on Friday. That would put it on track to surpass the current record high deficit, which was 1.6 trillion yen in January 2013. The finance ministry will release trade data for all of January on Feb. 20. Exports rose 11.3 percent in the first 20 days of January, compared with the same period a year ago. Imports, however, jumped an annual 30.2 percent. The yen has fallen around 23 percent versus the dollar since late 2012 as Prime Minister Shinzo Abe's government embarked on a bold plan to end 15 years of deflation with expanded quantitative easing from the Bank of Japan. The yen's decline has helped consumer prices rise as it pushes up import costs, which is contributing toward reaching the Bank of Japan's 2 percent inflation target. Many in the government also expected the yen's fall to boost exports, but this has largely failed to materialise as Japanese companies are producing more goods outside of the country. Growing signs of weakness in emerging market countries has also raised concerns that demand for Japanese exports could deteriorate further. The economy is likely to boom until March as consumers rush to beat the sales tax hike, and many analysts agree with the BOJ's view that the pain from the higher tax will be temporary. However, weak exports could mean that the rebound is slower than some economists anticipate.