On Thursday night, North Korea test-fired another one of its intermediate range missiles over Japan.

The rogue state has conducted other launches before, but CBS News national security correspondent David Martin reports that this test marks a big advance: until now, North Korea had tested its intermediate and intercontinental range missiles from fixed launch pads.

This time, for the first time, an intermediate range missile was launched from a mobile transporter, a significant development since it enables Kim Jong Un to fire a long-range weapon with little or no warning.

In this case, though, spy satellites had seen the missile being rolled into position at an airfield near Pyongyang well before the actual launch, as if Kim was deliberately trying to avoid catching the U.S. off guard.

The missile flew more than 2,000 miles over northern Japan and into the Pacific Ocean. A Pentagon official said it was "no coincidence" the missile flew far enough to reach the U.S. air base on Guam had it been fired in that direction.

The launch came three days after the U.N. Security Council enacted new economic sanctions against North Korea. But it is becoming increasingly clear sanctions will not work fast enough to prevent North Korea from acquiring a nuclear arsenal.

Earlier this week, a Treasury Department official showed Congress how easily North Korea evades the ban on coal exports.

In June, a ship left port in China. Halfway to North Korea it turned off the transponder which allows it to be tracked. It pulled into North Korea, where it was seen by a satellite as it loaded coal.

The ship returned to the point where it had turned off the transponder, switched it back on and proceeded to a port in Russia, leaving a track which looked like it had gone straight from China to Russia.

Those new sanctions aim to cut North Korea's oil imports, but CBS News Asia correspondent Ben Tracy reports that they will not have much bite.

China supplies 90 percent of North Korea's oil, and it has already cut some supplies. But the new sanctions cap supply at current levels, about 4 million barrels a year. That is likely enough to supply the North Korean military with what it needs.

The idea that China can call up Kim Jong Un and tell him to cut it out is not realistic. China and North Korea do not have a good relationship right now, Tracy reports.

As worried as it may be about a nuclearized Korean Peninsula, China does not want to see the North Korean regime collapse. Nor does it want a united Korea aligned with the West, which could mean the U.S. military on its border.

Bottom line, Tracy says: China wants to do enough to bring North Korea to the negotiating table but not enough to bring it to its knees.

U.S. and U.N. officials say the only step that will make sanctions work is to give navies the power to stop and search vessels suspected of carrying banned goods to and from North Korea.