Verizon Communications Inc said 45,000 striking workers in the northeast US will begin returning to the job tonight, while the two sides keep negotiating what the company called \"major issues.\" Benefits, work flexibility and job security are among the matters that still need to be negotiated, Verizon said in a statement yesterday. Contracts that expired on August 6 will remain in effect for an undefined period, Verizon said. Facing a decline in its traditional landline phone business, Verizon has been seeking work-rule changes and employee contributions to health-insurance premiums. Workers have said they shouldn\'t have to make substantial concessions as earnings rise and executive pay remains healthy. \"This is going to take time, that\'s why there was no set deadline,\" said Peter Thonis, a spokesman for Verizon, in a telephone inter View. \"We will be meeting again very soon. There is a set schedule for this.\"