The World Cup takes place in Australia in 2008 and qualifying is already well under way.
Holders Australia, New Zealand, England, France and Papua New Guinea are automatic qualifiers, leaving another five places up for grabs.
Tonga became the first team to book their place after downing Samoa in the final match of the Pacific group, with Fiji qualifying as runners-up.
The champions of the two European groups, and the winner of the repechage round also qualify.
Samoa are through to the repechage after failing to finish in the top-two positions in their group.
They are joined by the United States, who beat Atlantic Group rivals Japan 54-18 on Saturday.
Tonga became the first team to qualify from the group stages after beating Samoa 18-10 in the final match of the Pacific group.
The Tongans' victory means runners-up Fiji also go through to the main draw.
Samoa, who beat Fiji and the Cook Islands in earlier group matches, lost out on automatic qualification on points difference but could make the finals from the repechage.
Tonga 56-14 Cook Islands
Samoa 30-28 Fiji
Fiji 30-28 Tonga
Samoa 46-6 Cook Islands
Fiji 40-4 Cook Islands
Tonga 18-10 Samoa
The United States beat Japan 54-18 to qualify for the repechage.
The two teams were the only ones left in the group after South Africa and the West Indies withdrew.
USA 54-18 Japan
European qualifying has already begin with Russia and Georgia both making it through round one.
Georgia were subsequently expelled from the competition, which means only Russia advanced.
In round two, Ireland and Lebanon are vying for top spot in their group.
After victories over Russia, they shared an 18-18 draw a Dublin's Tolka Park on Sunday, 5 November.
In the other pool, Scotland are in pole position after a 21-14 success over Wales.
The winners of each group will qualify for the World Cup while the runners-up will go through to the repechage round.
Russia 40-14 Netherlands
Georgia 45-10 Serbia
Georgia 57-16 Netherlands
Russia 44-6 Serbia
Netherlands 38-26 Serbia
Russia 24-0 Georgia
Wales 14-21 Scotland
Scotland v Wales (3/4 Nov 2007)
Russia 12-50 Ireland
Lebanon 22-8 Russia
Ireland 18-18 Lebanon
Ireland v Russia (20/21 Oct 2007)
Russia v Lebanon (27/28 Oct 2007)
Lebanon v Ireland (3/4 Nov 2007)