Asian countries are set to sign an agreement at a United Nations meeting in Shanghai that will set up a pan-Asian highway.

The U.N. Economic and Social Commission for Asia and the Pacific expects that about 20 countries will sign up for the agreement during its week-long gathering that kicked off on Thursday. The Asian Highway Agreement will enter into force 90 days after eight countries have signed it.

The agreement calls for building a 140 thousand kilometer network of roads linking St. Petersburg to Singapore and Seoul to Istanbul that supporters hope will spur economic development across the continent.

Last November the 32 countries participating in the Asian Highway network agreed in principle to the inter-governmental agreement, but each country still has to individually approve it.

The agreement is necessary partly to determine the details of the network, from mapping precise itineraries to ensuring that each one of the 55 approved routes is up to standards.

Two out of the 55 routes would pass through South Korea.

The network is already about 83 percent completed, but will require some new construction as well as improvements along the remaining 17 percent of its length.

The 62-nation agency has been campaigning for a trans-Asian highway system since 1959, but substantial work on the project has coalesced only in the past three years.