WASHINGTON — Mexican President Carlos Salinas de Gortari Saturday said he and President Bush have agreed to conclude a free trade agreement as soon as possible, but declined to speculate on the key issue of timing.During three hours of talks with Bush at the presidential retreat in Camp David, Md., the two leaders "ratified the political commitment to have a free trade agreement, and to have it soon," President Salinas told reporters. But Salinas declined to answer questions on whether he had obtained a firm commitment from Bush that the White House would send the pact to Congress for consideration this year. The Mexican stock exchange plunged this week over fears that the pact could be postponed because of critics in the United States who argue that it might speed up the exodus of American firms to Mexico in search of cheaper labor. Both Salinas and the White House said that was not the case. They said the free trade pact would benefit Mexico, the United States, and Canada, which is also party to the talks. The accord would create a free trade area with $6 trillion in yearly output and 360 million consumers. Prospects of free trade with the US and Canada have attracted trade and investment to Mexico, but experts say those benefits could quickly dry up without a pact. The two presidents also agreed to intensify cooperation on the anti-drug fight and to seek a solution to the problem of illegal immigration of Mexicans searching for jobs. At a dinner put on Friday night in his honor by US Secretary of State James Baker III, Salinas repeated his belief that free trade could help alleviate the illegal immigration problem. "We want to export goods, not people," Salinas said.