The Federal Reserve yesterday told Congress it expects some pickup in economic growth in coming months and indicated it will continue to accommodate the nation's demand for money and credit in an effort to help make it happen.

The semiannual report on monetary policy by the Fed's policy-making group, the Federal Open Market Committee (FOMC), implied that, unless the economy does speed up somewhat, further interest-rate cuts are likely, financial analysts said.

FOMC members expect the economy to grow at a rate of 2 1/2 to 3 percent between the fourth quarter of 1985 and the fourth quarter of this year, the report said. Inflation is projected at between 2 1/4 and 2 3/4 percent over the same period, as measured by the gross national product price index.

For 1987, the members predicted an increase in GNP, after adjustment for inflation, of between 3 and 3 1/2 percent, which would be enough to produce a modest decline in unemployment, the report said. "A significant portion of the increase in production next year is expected to come from the external trade sector, with the lower value of the dollar expected to restrain the growth of imports and stimulate exports," it added.

The Reagan administration will release its revised forecast early next month. It is expected to show about 4 percent growth for the rest of the year and still faster growth in 1987.

Like the Fed, many private forecasters still expect faster economic growth later this year as a result of previous interest-rate declines, lower oil prices and drops in the value of the U.S. dollar.

However, recent economic statistics give no indication that such a pickup has begun, and some economists are scaling back their growth predictions. For example, Donald Straszheim, chief economist at Merrill Lynch, yesterday said the giant brokerage firm now believes there will be little, if any, growth in the second half of this year, much less any acceleration from the slow pace of the first six months.

According to the Fed report, at a meeting earlier this month, the FOMC reaffirmed its money growth targets for 1986 but decided largely to disregard increases in one measure of money, M1, which has been growing far faster this year than the central bank intended. M1, formerly the most closely watched of several monetary aggregates targeted by the Fed, includes currency in circulation and checking account deposits.

The report said the key to faster economic growth is a reduction in the nation's huge trade deficit. With such a large share of U.S. demand for goods being supplied from abroad, production in this country is hurting, the report said. "With little observed pickup in demand, many firms have scaled back their expenditure plans, and capital spending remains weak as a result," it said.

Meanwhile, some other parts of the economy, such as the service sector, are doing well. Still others, including agriculture and energy, are under increasing pressure, the report said.

"What monetary policy has been able to do during a period of greater overall price stability and adequate production capacity relative to the demands actually placed upon it is to accommodate demands for money and credit, helping to facilitate further declines in interest rates," the report continued.

"Monetary policy by itself cannot eliminate or deal with the sectoral imbalances that are still troubling the economy," it said.

"The committee believes that the monetary objectives it has set are supportive of a strengthening of economic activity in the second half of the year. However, the uncertainties associated with the economic outlook appear to be quite large, and continued vigilance and flexibility in the conduct of policy clearly are needed," the report declared.

Analysts interpreted this as a commitment by the Fed to seek lower interest rates -- on top of the cuts of 1 1/2 to 2 percentage points in most rates already this year -- if economic growth does not increase.

The report, which is required by the Full Employment and Balanced Growth Act of 1978, known as the Humphrey-Hawkins Act, was sent to the Senate and House banking committees. Fed Chairman Paul A. Volcker will testify about it Wednesday before the Senate committee.

Volcker is certain to be questioned closely about the economic outlook, particularly with forecasts such as that from Merrill Lynch suggesting there will be no growth for the rest of the year.

Merrill Lynch's Straszheim said strong consumer spending and housing construction will not be enough to move the economy ahead during the rest of the year. He also said business spending on new plant and equipment is likely to be weak over the next year, and the hoped-for lift to U.S. manufacturing from the dollar's decline in foreign-exchange markets remains a way off.

The report explained that the FOMC decided, in effect, not to worry about the above-target M1 growth for the rest of the year, because of an "extraordinary" break in the normal link between changes in M1 and later changes in economic activity. Technically, it reaffirmed its earlier 3 to 8 percent target range for M1 growth, but said that faster growth would be acceptable.

The committee also reaffirmed its 6 to 9 percent targets for growth of two broader monetary aggregates, M2 and M3, for 1986. Both those money measures are well within their target ranges.

For 1987, the FOMC tentatively kept the same target range for M1 but left open the question of whether much attention would be paid to it.