The New York Times says the United States is closely watching recent signs that North Korea is preparing to test a nuclear weapon.

The paper said U-S officials are examining satellite photos apparently showing increased activity at the North's suspected nuclear sites, including the construction of a reviewing stand, presumably for dignitaries.

Bush administration officials, however, say North Korean leader Kim Jong-il may be staging the activity to secure better economic and diplomatic incentives from the United States.

The report says Washington has briefed South Korea and Japan on the North's signs.

Since October, U-S intelligence has spotted periodic nuclear activity in the North, mostly in its northeastern area near Gilju, but the daily says preparations have apparently accelerated in recent weeks.

Several U-S officials were quoted as saying the North's preparations in recent days are the most advanced they have seen.