* Dollar rebounds from seven-week low
* Dollar gains vs yen as BOJ increases medium-term JGB purchases
* Little reaction to better-than-expected Japan CPI, U.S. GDP next
* Mexican peso falls as Trump proposes big tax on Mexican goods
By Yuzuha Oka
TOKYO, Jan 27 (Reuters) - The dollar perked up on Friday, rebounding from a seven-week low on optimism over the U.S. economic outlook and corporate earnings, while the Mexican peso fell after the White House floated the idea of a 20 percent tax on Mexican goods to pay for a border wall.
The dollar index .DXY , which measures the greenback against six major peers, gained 0.2 percent to 100.57. The index had recovered overnight to hit 100.73, after dipping to a seven-week low of 99.793.
"The dollar was helped by rising U.S. Treasury yields and strong equities," said Minori Uchida, chief FX analyst at Bank of Tokyo Mitsubishi UFJ.
"Trump has signed several executive orders since his inauguration, showing continuity from his campaign days, so the markets expect him to go ahead with the fiscal stimulus as well," Uchida added.
While U.S. equities and Treasury yields have extended their gains in the past week, fuelled by a positive U.S. economic outlook and President Donald Trump's signals of new public spending, concerns over potentially new trade barriers have weighed on the dollar in the last two weeks.
The dollar index is on track to lose 0.2 percent this week. It has weakened for two consecutive weeks since the beginning of this year.
Investors were also concerned about Trump's plans to construct a U.S.-Mexican border wall to stem illegal immigration.
The White House said on Thursday that Trump proposed a new 20 percent tax on goods from Mexico to pay for the wall. Mexican peso MXN=D2 fell 0.6 percent against the dollar following the news, and stepped back from Thursday's three-week high of 20.8645. It last stood at 21.35.
"The tax on Mexican imports will undermine consumer purchasing power and could eventually cast a shadow on the U.S. economy," said Makoto Noji, senior strategist at SMBC Nikko Securities.
"A protectionist stance adding to tensions between trade partners will not be positive for stocks and the dollar in the long term," Noji said.
The dollar gained 0.4 percent against the yen to 114.96 yen JPY= . The greenback rose to a high of 115.04 yen earlier on Friday after the Bank of Japan announced an increase in five- to ten-year Japanese Government bonds purchases and helped bring down yields from 11-month highs BOJ's move added to the widening of U.S.-Japan interest rate differentials which has boosted the dollar since the U.S. election.
The U.S. 10-year Treasury yield last stood at 2.515 percent US10YT=RR , while the 10-year JGB yield was at 0.070 percent JP10YTN=JBTC , down 1.5 basis points on the day.
The yen showed limited response to a slightly better-than-expected reading in Japan's consumer price index (CPI) data. The core CPI fell 0.2 percent from a year earlier in December, less than economists' forecast of a 0.3 percent fall. euro last stood at $1.0679 EUR= against the greenback, not far from Thursday's low of $1.0658.
The euro was on track to lose 0.2 percent this week, after gaining for two consecutive weeks since the start of the year.
Investors' focus is now on U.S. fourth-quarter gross domestic product estimates due later in the day. ECONUS
Sterling was fetching $1.2582 GBP=EBS , and is on track to gain 1.8 percent for the week. It gained 5 percent in two weeks, recovering from a three-month low of $ 1.1983 hit on Jan. 16.
British Prime Minister Theresa May will be the first foreign leader to meet the new U.S. President later in the day. May called on Trump to renew the "special relationship," expecting a rapid trade deal and close economic ties between the two countries. by Jacqueline Wong & Shri Navaratnam)