* U.S. Q4 GDP growth 2.1 percent in final estimate
* Yield rise seen temporary (Adds comment, updates prices)
By Gertrude Chavez-Dreyfuss
NEW YORK, March 30 (Reuters) - U.S. Treasury debt yields rose on Thursday after the final fourth-quarter U.S. gross domestic product number was revised higher, reflecting steady but less spectacular growth than in the prior quarter for the world's largest economy.
"We are positive on U.S. economic growth and underlying fundamentals but we don't see economic growth jumping to 3 percent," said Chris Molumphy, chief investment officer at Franklin Templeton's fixed income group in San Francisco.
"And in that environment, we will have slightly higher rates, but not significant."
Yields have trended lower over the last two weeks, with that of benchmark U.S. 10-year notes declining roughly 30 basis points since hitting a three-month peak on March 14. Analysts said the slight gain in Thursday's yields, which move inversely to prices, could be temporary.
Data showed that U.S. GDP grew 2.1 percent in the fourth quarter, higher than the second estimate of 1.9 percent growth and exceeding market forecasts for a 2.0 percent rise. The final number, however, was less than the 3.5 percent rise in the third quarter.
In late trading, benchmark 10-year notes fell 9/32 in price to yield 2.419 percent, compared with 2.387 percent late on Wednesday.
U.S. 30-year bond prices fell 24/32, yielding 3.031 percent US30-YT=RR, up from Wednesday's 2.994 percent.
On the front end of the curve, U.S. two-year note yields were at 1.285 percent, up from 1.278 percent on Wednesday.
Treasuries have been rising the last two weeks after the Federal Reserve at its last policy meeting stuck to its forecast for three interest rate increases this year.
More recently, growing doubts about the Trump administration's ability to get anything done to bolster the economy have also pushed Treasury prices higher.
After Republicans on Friday withdrew their bill to replace and repeal Obamacare due to lack of support in Congress, some investors believe the next big reform, on taxes, could face tough challenges as well.
Molumphy of Franklin Templeton said economy-boosting tax reform had a good chance of being passed. "However, it's likely to be smaller in size than what the market is anticipating and also further out into the future."
Molumphy said the impact of tax reform on the economy would probably not show up until 2018 or later. (Reporting by Gertrude Chavez-Dreyfuss; Editing by Andrea Ricci and Richard Chang)