* S.Korea's trade minister to depart for United States on Tuesday
* S.Korea to decide whether or not to joint CPTPP within H1 (Adds S.Korea's trade minister's visit to U.S.)
SEOUL, March 12 (Reuters) - South Korea will "deploy all possible means" to respond to U.S. President Donald Trump's decision to impose tariffs on steel and aluminium imports, the country's finance minister said.
Last week, Trump pressed ahead with steep import tariffs of 25 percent on steel and 10 percent for aluminium, but exempted Canada and Mexico and offered the possibility of excluding other allies, backtracking from an earlier "no-exceptions" stance.
South Korea, the third-largest steel exporter to the United States and a strategic ally on the Korean peninsula, has already put in a request for a waiver.
"We will make clear what our stance is," Finance Minister Kim Dong-yeon said on Monday during a policy meeting in Seoul.
"(The government) will deploy all possible means to respond to U.S. steel tariffs measures and make an all-out effort," he added, without elaborating.
South Korea's minister for trade, Kim Hyun-chong, who has visited the United States twice in recent weeks to seek ways to minimise the damage to South Korean steelmakers, will depart for the United States on Tuesday, a ministry spokeswoman said.
South Korea's government will also decide on whether to join the Comprehensive and Progressive Trans-Pacific Partnership within the first half of this year, Kim said at the meeting.
Eleven countries, including Japan and Canada, have signed the landmark Asia-Pacific CPTPP trade agreement without the United States in what one minister called a powerful signal against protectionism and trade wars.
"The government has been reviewing economic validity of CPTPP, and will draw agreement between the related government agencies about joining it within the first half," Kim said. (Reporting by Shin-hyung Lee, Cynthia Kim, Dahee Kim; Additional reporting by Jane Chung; Editing by Dwarakanath and Himani Sarkar)