BRUSSELS, SEPT. 10 -- Secretary of State James A. Baker III announced plans today to make the first high-level American visit to Syria in more than two years in order to confer with President Hafez Assad and further isolate Iraqi President Saddam Hussein.

Baker also said the Bush administration has made overtures through third parties to Iran, which like Syria is a long-standing enemy of Iraq, about improved relations. He said the time had not yet come for a visit to Tehran or normalization of relations, but he indicated interest in better ties with Tehran as a means of squeezing Iraq.

In Tehran today, Iraqi Foreign Minister Tariq Aziz completed a visit to Iran with an announcement that the recently warring neighbors would resume diplomatic relations. Saddam, meanwhile, in a move that could strain international support for the U.N. embargo against Iraq, offered free oil to any Third World country that can find shipping to transport it.

Baker was in Brussels to inform NATO foreign ministers about Sunday's meeting in Helsinki between President Bush and Soviet President Mikhail Gorbachev and to urge European countries to contribute troops to the U.S.-led force defending Saudi Arabia against Iraq. He received assurances of logistical support but no new commitments of ground forces. {Stories, Page A7.}

Syria -- which has committed troops to an Arab force backing the Saudis -- and Iran have long been considered outlaw nations by the United States. Both remain on the State Department's list of countries that have sponsored terrorism. The U.S. overtures toward them appeared to be part of a strategy involving incremental measures to turn up the heat on Saddam -- from expelling some Iraqi diplomats from Washington to consulting with Saddam's enemies.

Baker, asked the purpose of his Damascus trip planned for Thursday, said he would seek Assad's "assessment" of the Persian Gulf crisis and his "view particularly of the other Arab" states. Baker said Bush "felt simply that it was an important time" for contact with Syria.

While the point of Baker's visit may be nothing more than to make Saddam worry about what the international community is planning against him, the U.S. secretary appeared somewhat uncomfortable in announcing the trip. Reporters who had heard that Baker was planning to go to Damascus were told by a State Department official that the secretary would not disclose plans for the trip unless asked. It was the first question at a press conference here today following the NATO meeting.

According to the State Department's recent publication, "Patterns of Global Terrorism," Syrian leaders have not supported terrorism outside Lebanon for several years, but "continue to provide support and safe haven to a number of groups that engaged in international terrorism."

Among them are the Popular Front for the Liberation of Palestine-General Command, led by Ahmed Jabril, a former captain in the Syrian army. The group has been linked in news reports to the December 1988 bombing of Pan Am Flight 103, in which 270 people were killed.

According to the State Department report, the U.S. government "is not satisfied with the Syrian government's responses" to concerns about terrorism "and we think the Syrian government can do more." However, the report also noted that Syria has "made some effort to improve its record as a state sponsor of terrorism" through efforts to facilitate the release of American hostages held by pro-Iranian extremist groups in Lebanon.

No official of Baker's stature has visited Syria since a trip by Secretary of State George P. Shultz just before the Pan Am 103 disaster. Earlier in the Reagan administration, when Marines were deployed in Lebanon, Syria shot down two Navy fliers on a reconnaisance flight. The USS New Jersey battleship then shelled Syrian-held positions in the Lebanese highlands.

The Bush adminstration's policy has generally been to isolate Syria, but earlier this year Bush praised its role in helping win the release of an American hostage, and the relationship thawed further when Assad committed troops and support for the isolation of Saddam.

Baker said today that the time had come for "face-to-face discussions" with Syria's president on "how we might be able to cooperate to achieve what happen to be mutual goals."

Baker noted that "some of the gulf countries have already made certain commitments" to help Syria as a result of its dispatch of troops. He was not specific but in the past Saudi Arabia has sent aid to Damascus.

By turning to Syria, the Bush administration appears to be trying to take advantage of years of hatred between Assad and Saddam, who come from rival factions of the secular Baath Party. Syria actively aided Iran during its eight-year war with Iraq, and Saddam more recently shipped weapons to Christian militia forces in Lebanon who were fighting Syrian-backed factions.

"It is very important, it seems to me, in a situation such as we have in the gulf, that we cooperate with a major Arab country who happens to share the same goals that we do," Baker said. "That does not mean that . . . the formally strained relations are cured overnight and doesn't mean that we won't continue to have some differences." But "on this very, very important issue of what happens to reverse Iraq's unprovoked aggression, we share the same goals."

When questioned about Syria's involvement with terrorists and human rights abuses, Baker responded, "I'm simply saying, they're there." Asked if he was concerned about the implications of closer ties with Damascus, Baker said, "We are going to sit down and talk to them face to face just as we talked to a number of governments with whom we have less formal relations than we do with Syria." He added: "We are talking to Vietnam. We are talking to Phnom Penh. We are talking to a lot of people for a lot of different reasons."

Baker said he would raise with Assad the presence of terrorist groups in Syria. "We will continue to talk to the Syrians" about the Popular Front for the Liberation of Palestine-General Command, he said, "and we will continue to share with them the difficulties we have with the presence of that group in Syria and the difficulties we have with that group itself."

Asked if he was concerned about the symbolism of such contacts at a time when the United States is trying to establish a moral high ground above Saddam, Baker replied, "The answer is, not in the least." He added: "We are not embracing Syria and everything that Syria has done with which we disagree. We will continue to disagree and we will air those disagreements during the course of this visit."

Baker offered a similar rationale for reaching out to Iran, although other officials cautioned that the prospects of improved relations are dim as long as American hostages are being held in Lebanon by Iranian-backed extremist groups.

"Would we welcome anything Iran could do to assist in the isolation of Saddam Hussein? You bet we would," Baker said. "Has that been communicated to Iran? You bet it has. Would we go to Tehran today? No. We do not have relations at all with Iran for reasons that are very well-known. We do have relations, albeit not good ones, with Syria."

State Department spokesman Margaret Tutwiler said Baker had informed Israeli Foreign Minister David Levy, when they met last week, about his plans to go to Syria.

According to a senior administration official in Washington, Bush has had at least three telephone conversations with Assad and several written communications since the gulf crisis began.

Baker also added some detail to his suggestion last week for creation of a "regional security structure" for the gulf. When the current crisis is over, he said, the international community will have to find internationally approved measures to bar Saddam from obtaining or stockpiling weapons of mass destruction. He suggested strengthening the nuclear nonproliferation treaty to keep "an outlaw like Saddam" from obtaining nuclear weapons.

Some members of Congress have advocated a military strike to disable Saddam's nuclear- and chemical-weapons programs, but the administration has been vague about whether it would be willing to go that far.