By Kim Rahn

President Moon Jae-in is toughening his policy toward North Korea as the Kim Jong-un regime intensifies its provocations.

At the same time, U.S. President Donald Trump's apparent complaints about what his aides call Moon's "soft" stance are reducing his room to maneuver.

Moon's offers for dialogue have met with Pyongyang's continuous missile launches and a nuclear weapon test.

He is therefore expected to focus on sticks rather than carrots ― at least for now ― while building up the South's military capability.

In a phone call with Trump, Moon emphasized the need for a whole new level of strong and effective countermeasures which can put real pressure on North Korea.

As part of such countermeasures, Moon and Trump agreed to remove weight limits on South Korea's missile warheads to boost Seoul's own defense capabilities against North Korea's threats.

The two leaders made the agreement during the phone conversation Monday night, which came a day after Pyongyang conducted its sixth nuclear test with what it claimed was a hydrogen bomb.

Moon asked for the lifting of the limits, which had been previously set by the allies' missile guidelines, according to Cheong Wa Dae Tuesday.

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What was conspicuous in the press briefing about the Moon and Trump phone conversation was the lack of mentioning of the need for dialogue to resolve the impasse, an indication that Moon is shifting toward a hard-line stance.

The President is seeking to have Korea build its own nuclear-powered submarines to counter threats from Pyongyang's submarine-launched ballistic missiles.

He talked about the issue to Trump during an earlier phone conversation Aug. 7, and Defense Minister Song Young-moo also mentioned it as effective preparedness during his meeting with U.S. Defense Secretary James Mattis last week.

The government is also likely to complete the temporary deployment of four additional launchers of a U.S. Terminal High Altitude Area Defense (THAAD) battery in Seongju, North Gyeongsang Province, within this week.

With two launchers already put into operation under the former Park Geun-hye administration, Moon, citing procedural flaws, initially decided to delay the full deployment until a full-scale environmental impact assessment was completed.

But he changed his position and ordered the installation of the remaining launchers July 29 after Pyongyang fired an intercontinental ballistic missile.

The environment ministry conducted a small-scale survey and approved the temporary deployment Monday. The defense ministry and the U.S. Forces Korea are planning to deploy the launchers as soon as possible.

The deployment will draw a stronger backlash from China, which claims the THAAD radar will be used to spy on its military activities. However, Moon appears to be giving priority to enhancing deterrence against North Korea regardless of more serious economic retaliation from China.

Moon also urged for a new U.N. Security Council (UNSC) resolution to impose stronger sanctions on Pyongyang, during a phone conversation with Russian President Vladimir Putin. He proposed halting oil supplies to North Korea as well as cutting off its sources of foreign currency, including banning it from "exporting" workers.

An oil embargo is seen as the strongest pressure on the North, which is why Moon mentioned this to Putin, as Russia is one of the five permanent members of the UNSC. Russia and China, North Korea's only ally and another UNSC permanent member, have opposed halting oil supplies.