Lebanon's foreign minister said yesterday he came to the United States with "one thing on my mind" -- to get the U.S. government to pressure Israel to withdraw its troops from his war-torn country. He said the continued presence of foreign forces in Lebanon is why it is now in the throes of a new round of sectarian fighting.

Elie Salem, the foreign minister, expressed strong fears that if the current stalemate over negotiations for withdrawal of foreign troops continues, Israel might effectively annex a portion of southern Lebanon.

"I am a son of a bitch who has been burned by history, and I'm afraid of new facts arising as the result of delayed action," he said. "It will be horrible. Already some people are referring to the southern part of Lebanon as the 'North Bank' of Israel . That is no joke to us."

Speaking to reporters and editors of The Washington Post shortly before he met yesterday with President Reagan, Salem said Syrian and Palestine Liberation Organization officials have assured the Lebanese their forces will depart when Israel agrees to go.

But he indicated he believed a faction of the Israeli Cabinet was not interested in discussing withdrawal of their forces from Lebanon. The way to break the impasse, he said, is for the United States to bring pressure on the Begin government.

"I think America is in a position to deliver on anything America feels strongly about in the Lebanese-Israeli situation and nobody's going to convince me otherwise," he said. "I was not born yesterday. I would be furious if the U.S. does not deliver."

After meeting with Reagan, Salem said he was "very encouraged" and had "no doubt that the president is committed to a fair and equitable resolution of the Lebanese crisis."

Earlier, in the meeting at The Post, Salem acknowledged that in his three-day U.S. mission he has been seeking a commitment to increase the size of the Marine contingent in the 4,300-member multinational force in Beirut, now composed of U.S., Italian and French troops, to about 12,000 to 15,000 troops.

After his meeting with Reagan, White House deputy press secretary Larry Speakes said the matter "remains under serious consideration."

France agreed last weekend to increase the size of its forces in Lebanon, Salem said. British Foreign Secretary Francis Pym said in an interview in London yesterday with Washington Post correspondent Peter Osnos that Britain was "hopeful" of making a contribution to peace-keeping force in Lebanon. While stressing that British commitments to NATO, the Falkland Islands and elsewhere meant that any contribution would not be large, he said Britain would show its support for peace in Lebanon and the Middle East.

Salem said the Lebanese have also asked Colombia, Brazil and Portugal to contribute troops. He said they would be needed in Lebanon for eight months to a year after Israeli, Syrian and Palestinian troops withdraw to provide logistical backup for the Lebanese Army and to bring "the psychological security that cannot be easily defined."

U.S. special envoy Morris Draper met with Lebanese President Amin Gemayel in Beirut yesterday and reportedly proposed a partial pullback by Israeli, Syrian and Palestinian forces in central Lebanon as the first phase of a total withdrawal.

After the discussions, Draper flew to Jerusalem where he joined fellow U.S. diplomat Philip C. Habib. Their joint efforts appeared to be the beginning of a new effort at indirect "shuttle negotiations" aimed at getting the talks off the ground.

For weeks, the discussions have been delayed while Israeli and Lebanese officials haggled over the composition of negotiating teams and the location of the discussions. Salem said the Lebanese met all of Israel's other conditions but drew the line at holding some of the talks in Jerusalem. The Lebanese fear an adverse reaction in the Arab world, which does not recognize Jerusalem as the Israeli capital.

Salem said he believed that the prospects for future face-to-face talks between Israel and Lebanon were now "dead," although he did not object to a European proposal that talks be held somewhere in Europe.

Salem said the fighting in Tripoli in the area of northern Lebanon under Syrian control and in the Chouf, southeast of Beirut, under Israeli control, were spurred by the presence of the occupying forces.

"There are dangerous games being played," he said. "There is no sectarian strife in the areas where the Lebanese Army is in control."

On another matter, Salem said the Lebanese government has arrested 20 people in connection with the September massacres at the Palestinian camps, Sabra and Shatila. "Some are Lebanese. Some are not Lebanese," he said, declining to elaborate.