Answer:
Step-by-step explanation:
"The main obstacle to progress" means the primary barrier or difficulty that is preventing or hindering advancement, development, or improvement in a particular situation or context. In the given passage, it is suggested that Matsuoka, the Japanese foreign minister, is seen as the main obstacle to progress in the conversations between the United States and Japan, which were intended to resolve their differences and strengthen their relationship. Hull, the U.S. Secretary of State, singles out Matsuoka for criticism, suggesting that his "tantrums" are preventing progress and that the talks are increasingly being seen as a way to weaken the pro-Axis camp in Japan.